TCA cycle

Liver cancer is one of the most common cancer worldwide with a high mortality. Methionine is an essential amino acid required for normal development and cell growth, is mainly metabolized in the liver, and its role as an anti-cancer supplement is still controversial. Here, we evaluate the effects of methionine supplementation in liver cancer cells. An integrative proteomic and metabolomic analysis indicates a rewiring of the central carbon metabolism, with an upregulation of the tricarboxylic acid (TCA) cycle and mitochondrial adenosine triphosphate (ATP) production in the presence of high methionine and AMP-activated protein kinase (AMPK) inhibition. Methionine supplementation also reduces growth rate in liver cancer cells and induces the activation of both the AMPK and mTOR pathways. Interestingly, in high methionine concentration, inhibition of AMPK strongly impairs cell growth, cell migration, and colony formation, indicating the main role of AMPK in the control of liver cancer phenotypes. Therefore, regulation of methionine in the diet combined with AMPK inhibition could reduce liver cancer progression.

Aluminum (Al), a known environmental toxicant, has been linked to a variety of pathological conditions such as dialysis dementia, osteomalacia, Alzheimer's disease, and Parkinson's disease. However, its precise role in the pathogenesis of these disorders is not fully understood. Using hepatocytes as a model system, we have probed the impact of this trivalent metal on the aerobic energy-generating machinery. Here we show that Al-exposed hepatocytes were characterized by lipid and protein oxidation and a dysfunctional tricarboxylic acid (TCA) cycle. BN-PAGE, SDS-PAGE, and Western blot analyses revealed a marked decrease in activity and expression of succinate dehydrogenase (SDH), α α-ketoglutarate dehydrogenase (KGDH), isocitrate dehydrogenase-NAD + (IDH), fumarase (FUM), aconitase (ACN), and cytochrome c oxidase (Cyt C Ox). 13 C-NMR and HPLC studies further confirmed the disparate metabolism operative in control and Al-stressed cells and provided evidence for the accumulation of succinate in the latter cultures. In conclusion, these results suggest that Al toxicity promotes a dysfunctional TCA cycle and impedes ATP production, events that may contribute to various Alinduced abnormalities.

Background: Thyroid cancer is the most common endocrine malignancy, with papillary thyroid carcinoma (PTC) being the most common (85–90%) among all the different types of thyroid carcinomas. Cancer cells show metabolic alterations and, due to their rapid proliferation, an accumulation of reactive oxygen species, playing a fundamental role in cancer development and progression. Currently, the crosstalk among thyrocytes metabolism, redox balance and oncogenic mutations remain poorly characterized. The aim of this study was to investigate the interplay among metabolic alterations, redox homeostasis and oncogenic mutations in PTC-derived cells. Methods: Metabolic and redox profile, glutamate-cysteine ligase, glutaminase-1 and metabolic transporters were evaluated in PTC-derived cell lines with distinguished genetic background (TPC-1, K1 and B-CPAP), as well as in an immortalized thyroid cell line (Nthy-ori3-1) selected as control. Results: PTC-derived cells, particularly B-CPAP cells, h...

Bandara for their valuable suggestions, generous help, and friendship during the course of my stay in the lab. I would like to thank Joshua J Daniel and Vandhana Narayanan for helping me by proofreading my thesis. A special thanks to everyone for the wonderful brainstorming sessions during lab meetings, which made lab life a lot more fun and challenging.

Bandara for their valuable suggestions, generous help, and friendship during the course of my stay in the lab. I would like to thank Joshua J Daniel and Vandhana Narayanan for helping me by proofreading my thesis. A special thanks to everyone for the wonderful brainstorming sessions during lab meetings, which made lab life a lot more fun and challenging.

Objective: Effect of oleanolic acid against hexavalent chromium-induced altered brain energy metabolism associated with oxidative stress was evaluated in the present study. Methods: Swiss albino mice were divided into three groups, Control (n=6), chromium-treated (n=6), and oleanolic acid (OA) supplemented (n=6). The chromium treated group was orally administered with K2Cr2O7 for 30 days at a dose of 10 mg/kg b.w/day. OA supplementation was given at a dose of 5 mg/kg bw/day for the past 14 days of chromium treatment. Control group received the vehicle only. After the treatment, whole brain was removed for examining the parameters such as pyruvic acid, free amino nitrogen, tissue protein, TCA cycle enzyme activities, NADH dehydrogenase function, and oxidative stress markers. Results: Significant decrease in cerebral pyruvic acid content associated with suppressed malate dehydrogenase and succinate dehydrogenase activities were observed. The NADH dehydrogenase activity was inhibited o...

Plasma levels of branched-chain amino acids (BCAA) are consistently elevated in obesity and type 2 diabetes (T2D) and can also prospectively predict T2D. However, the role of BCAA in the pathogenesis of insulin resistance and T2D remains unclear. To identify pathways related to insulin resistance, we performed comprehensive gene expression and metabolomics analyses in skeletal muscle from 41 humans with normal glucose tolerance and 11 with T2D across a range of insulin sensitivity (SI, 0.49 to 14.28). We studied both cultured cells and mice heterozygous for the BCAA enzyme methylmalonyl-CoA mutase (Mut) and assessed the effects of altered BCAA flux on lipid and glucose homeostasis. Our data demonstrate perturbed BCAA metabolism and fatty acid oxidation in muscle from insulin resistant humans. Experimental alterations in BCAA flux in cultured cells similarly modulate fatty acid oxidation. Mut heterozygosity in mice alters muscle lipid metabolism in vivo, resulting in increased muscle...

4-Hydroxyisoleucine (HIL) found in fenugreek seeds has insulinotropic and anti-obesity effects, and is expected to be a novel orally-active drug for insulin-independent diabetes. Here we show that newly isolated strain Bacillus thuringiensis 2e2 and the closely related strain B. thuringiensis ATCC 35646 operates a novel metabolic pathway for L-isoleucine (L-Ile) via HIL and 2-amino-3-methyl-4-ketopentanoic acid (AMKP). The HIL synthesis was catalyzed stereoselectively by an α-ketoglutaric acid-dependent dioxygenase and to be useful for efficient production of a naturally occurring HIL isomer, (2S,3R,4S)-HIL. The (2S,3R,4S)-HIL was oxidized to (2S,3R)-AMKP by a NAD +-dependent dehydrogenase. The metabolic pathway functions as an effective bypass pathway that compensates for the incomplete TCA cycle in Bacillus species and also explains how AMKP, a vitamin B 12 antimetabolite with antibiotic activity, is synthesized. These novel findings pave a new way for commercial production of HIL and also for AMKP. Keywords L-Isoleucine dioxygenase • 4-Hydroxyisoleucine •NAD +-dependent dehydrogenase • 2-amino-3-methyl-4-ketopentanoic acid • Bacillus thuringiensis • TCA cycle

Background: Thyroid cancer is the most common endocrine malignancy, with papillary thyroid carcinoma (PTC) being the most common (85–90%) among all the different types of thyroid carcinomas. Cancer cells show metabolic alterations and, due to their rapid proliferation, an accumulation of reactive oxygen species, playing a fundamental role in cancer development and progression. Currently, the crosstalk among thyrocytes metabolism, redox balance and oncogenic mutations remain poorly characterized. The aim of this study was to investigate the interplay among metabolic alterations, redox homeostasis and oncogenic mutations in PTC-derived cells. Methods: Metabolic and redox profile, glutamate-cysteine ligase, glutaminase-1 and metabolic transporters were evaluated in PTC-derived cell lines with distinguished genetic background (TPC-1, K1 and B-CPAP), as well as in an immortalized thyroid cell line (Nthy-ori3-1) selected as control. Results: PTC-derived cells, particularly B-CPAP cells, h...

We have reported that the copper tolerant brown-rot fungus, Fomitopsis palustris, acquires metabolic energy by use of the constitutively-occurring Kornberg's glyoxylate cycle coordinating with oxalate biosynthesis and glucose oxidation (Erman Munir et al. Proc. Natl. Acad. Sci. USA, (2001) 98, 11126-11130). Furthrmore, this fungus does not have the normal TCA cycle, lacking 2-oxoglutarate dehydrogenase which is a key enzyme of the TCA cycle of most living things. This paper reports that most wood decay fungi tested lack 2-oxoglutarate dehydrogenase (ODH) and that much greater activities of glutamate dehydrogenase compensating the absence of ODH were detected from both white-and brown-rot fungi.

Recurrent urinary tract infections (UTIs) affect 10 to 40% of women. In up to 77% of those cases, the recurrent infections are caused by the same uropathogenic E. coli (UPEC) strain that caused the initial infection. Upon infection of urothelial transitional cells in the bladder, UPEC appear to enter a nongrowing quiescent intracellular state that is thought to serve as a reservoir responsible for recurrent UTIs. Here, we report that many UPEC strains enter a quiescent state when ≤10 6 CFU are seeded on glucose M9 minimal medium agar plates and show that mutations in several genes involved in central carbon metabolism prevent quiescence, as well as persistence, possibly identifying metabolic pathways involved in UPEC quiescence and persistence in vivo .

Acylglycerol kinase (AGK) is a mitochondrial lipid kinase that catalyzes the phosphorylation of monoacylglycerol and diacylglycerol to lysophosphatidic acid and phosphatidic acid, respectively. Mutations in AGK cause Sengers syndrome, which is characterized by congenital cataracts, hypertrophic cardiomyopathy, skeletal myopathy, exercise intolerance, and lactic acidosis. Here we identified AGK as a subunit of the mitochondrial TIM22 protein import complex. We show that AGK functions in a kinase-independent manner to maintain the integrity of the TIM22 complex, where it facilitates the import and assembly of mitochondrial carrier proteins. Mitochondria isolated from Sengers syndrome patient cells and tissues show a destabilized TIM22 complex and defects in the biogenesis of carrier substrates. Consistent with this phenotype, we observe perturbations in the tricarboxylic acid (TCA) cycle in cells lacking AGK. Our identification of AGK as a bona fide subunit of TIM22 provides an exciti...

In this study, we analyzed the toxic effect of Ni during the development of wheat shoots. Typical developmental alterations in carbon metabolism-related parameters reflecting changes associated with the transition of the seedlings from heterotrophic to autotrophic metabolism were observed in the control shoots between the 1st and the 4th days. Adverse effects of 50 and 100 M Ni became evident starting from the 4th day of growth on the metal-containing media. We found that Ni-induced stimulation of phosphoenolpyruvate carboxylase (PEPC) activity coincided with decrease in the ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) level and with declines in net photosynthetic rate (P N) and stomatal conductance (g s). Application of Ni resulted in increased activities of several dehydrogenases: glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), isocitrate dehydrogenase (NADP-ICDH) and malate dehydrogenase (NADH-MDH). In contrast, the activities of malic enzymes (NADP-ME and NAD-ME) decreased due to Ni stress. Treatment with Ni led to accumulation of glucose and declined concentration of sucrose as well as considerable increases in concentrations of malic and citric acids. Our results indicate that Ni stress redirects the carbon metabolism of developing wheat shoots to provide carbon skeletons for synthesis of amino acids and organic acids as well as to supply reducing power to sustain normal metabolic processes and to support defense mechanisms against oxidative stress.

Recurrent urinary tract infections (UTIs) affect 10 to 40% of women. In up to 77% of those cases, the recurrent infections are caused by the same uropathogenic E. coli (UPEC) strain that caused the initial infection. Upon infection of urothelial transitional cells in the bladder, UPEC appear to enter a nongrowing quiescent intracellular state that is thought to serve as a reservoir responsible for recurrent UTIs. Here, we report that many UPEC strains enter a quiescent state when ≤10 6 CFU are seeded on glucose M9 minimal medium agar plates and show that mutations in several genes involved in central carbon metabolism prevent quiescence, as well as persistence, possibly identifying metabolic pathways involved in UPEC quiescence and persistence in vivo .

Discovery of specific markers that reflect altered hepatic fatty acid oxidation could help to detect an individual's risk of fatty liver, type 2 diabetes and cardiovascular disease at an early stage. Lipid and protein metabolism are intimately linked, but our understanding of this crosstalk remains limited. Methods: In male Wistar rats, we used synthetic fatty acid analogues (3-thia fatty acids) as a tool to induce hepatic fatty acid oxidation and mitochondrial biogenesis, to gain new insight into the link between fatty acid oxidation, amino acid metabolism and TCA cycle-related intermediate metabolites in liver and plasma. Results: Rats treated with 3-thia fatty acids had 3-fold higher hepatic, but not adipose and skeletal muscle, expression of the thioesterase 3-hydroxyisobutyryl-CoA hydrolase (Hibch), which controls the formation of 3hydroxyisobutyrate (3-HIB) in the valine degradation pathway. Consequently, 3-thia fatty acid-stimulated hepatic fatty acid oxidation and ketogenesis was accompanied by decreased plasma 3-HIB and increased methylmalonic acid (MMA) concentrations further downstream in BCAA catabolism. The higher plasma MMA corresponded to higher MMA-CoA hydrolase activity and hepatic expression of GTP-specific succinyl-CoA synthase (Suclg2) and succinate dehydrogenase (Sdhb), and lower MMA-CoA mutase activity. Plasma 3-HIB correlated positively to plasma and hepatic concentrations of TAG, plasma total fatty acids, plasma NEFA and insulin/ glucose ratio, while the reverse correlations were seen for MMA. Conclusion: Our study provides new insight into TCA cycle-related metabolic changes associated with altered hepatic fatty acid flux, and identifies 3-HIB and MMA as novel circulating markers reflective of mitochondrial β-oxidation in male Wistar rats.

Aluminum (Al) is an important factor that limits plant growth under acidic soil conditions. However, several plant species developed distinct mechanisms that limit the damage caused by high Al concentrations. In highbush blueberry (Vaccinium corymbosum), the Al resistance mechanisms are not fully understood. This study was designed to evaluate the effect of Al toxicity on roots and leaves of highbush blueberry genotypes with contrasting Al resistance [Star (Al-sensitive) and Camellia and Cargo (Al-resistant)] and identify the main molecular and physiological strategies underpinning adaptive Al stress responses in nutrient solution. After 48 h of the Al treatment, the reduced form of ascorbate (ASC) was higher in roots, but unchanged in leaves of Cargo and Camellia genotypes compared to the control. We also observed decreased root exudation of oxalate in the Al-treated sensitive cultivar Star throughout the treatment period. However, in the resistant cultivar (Camellia), the exudation of oxalate increased 2.4-and 2.8-fold at 24 and 48 h, respectively, compared with t=0. The Al treatment affected differentially the enzyme activity and gene expression of the tricarboxylic acid (TCA) cycle enzymes. The NAD-dependent malate dehydrogenase (NAD-MDH) expression in roots of cultivar Cargo was reduced at 24 h and increased at 48 h, whereas in leaves the expression was higher at 24 h and decreased at 48 h compared to the control. The citrate synthase (CS) activity in Al-resistant Cargo roots diminished at 24 h, increasing afterwards, without variation in the CS gene expression, compared with t=0. In Al-resistant Camellia roots, the gene expression and the activity of CS decreased during Al exposure. NADP-dependent malate dehydrogenase (NADP-MDH) in the leaves of cultivar Cargo showed increased activity and gene expression at 24 h, whereas in roots the gene expression decreased, but the ratio of NADP-MDH initial/final activity increased. The expression of genes encoding enzymes of TCA cycle did not differ significantly in the Al-sensitive cultivar Star during Al exposure. In conclusion, the exudation of organic acid anions, particularly oxalate, plays an important role in Al resistance of highbush blueberry genotypes. In addition, increased concentration of ASC in roots, and a positive correlation between gene expression/enzyme activity of CS and NADP-MDH also contribute to the Al-resistance mechanisms exhibited by genotypes Camellia and Cargo.

Introduction: Polycystic ovarian syndrome (PCOS) is undoubtedly the commonest androgen disorder in woman's fertile period and certainly one of the most prevalent causes of anovulation. The syndrome has an estimated prevalence of 4%-10% among women of childbearing age. Previously, our group demonstrated the effect of gonadal white adipose tissue transplantation from wild-type lean and fertile female mice to isogenic obese anovulatory ob/ob mice. These complex metabolic interrelationships between obesity and PCOS have yet to be fully understood. The aim of this study was to evaluate the effect of gonadal white adipose tissue (WAT) transplantation from the wildtype lean and fertile female mice to isogenic obese, anovulatory mice (Lep ob/Lep ob) on the expression of glycolysis-and TCA cycle-related genes and obtain a general view of the glucose metabolism in the brain of these animals. Methods: Fifteen ob/ob mice ranging from 2 to 3 months of age were divided into 3 experimental groups: control normal weight (n = 5), obese control (n = 5) and obese 7 days leptin treated (n = 5). The whole brains of the mice were processed for RNA extraction. The samples from each group were used to perform PCR assays using an array plate containing 84 primers to study the glucose metabolism-related genes. Results: The glycolysis-and TCA cycle-related genes were significantly downregulated. The most significantly affected genes C. F. Baptista et al. 106 were as follows: for glycolysis (fold regulation with p < 0.05): Pgm1, Bpgm, Aldob, and Eno3 (119, 45, 18, and 28 times less, respectively); and for the TCA cycle (fold regulation with p < 0.05): Cs, Idh3b, and Mdh2 (84, 27, and 37 times less, respectively). Conclusion: The seven-day leptin treated mice show a decrease in the glucose metabolism. These results confirm the ability of the adipose tissue-derived hormone leptin to regulate early crucial genes that are related to glycolysis mechanisms and to the TCA cycle. This hormone seems to revert early the central physiological conditions that are associated with PCOS; however, the morphological alterations can only be observed within a 45-day treatment.

Introduction: Polycystic ovarian syndrome (PCOS) is undoubtedly the commonest androgen disorder in woman's fertile period and certainly one of the most prevalent causes of anovulation. The syndrome has an estimated prevalence of 4%-10% among women of childbearing age. Previously, our group demonstrated the effect of gonadal white adipose tissue transplantation from wild-type lean and fertile female mice to isogenic obese anovulatory ob/ob mice. These complex metabolic interrelationships between obesity and PCOS have yet to be fully understood. The aim of this study was to evaluate the effect of gonadal white adipose tissue (WAT) transplantation from the wildtype lean and fertile female mice to isogenic obese, anovulatory mice (Lep ob/Lep ob) on the expression of glycolysis-and TCA cycle-related genes and obtain a general view of the glucose metabolism in the brain of these animals. Methods: Fifteen ob/ob mice ranging from 2 to 3 months of age were divided into 3 experimental groups: control normal weight (n = 5), obese control (n = 5) and obese 7 days leptin treated (n = 5). The whole brains of the mice were processed for RNA extraction. The samples from each group were used to perform PCR assays using an array plate containing 84 primers to study the glucose metabolism-related genes. Results: The glycolysis-and TCA cycle-related genes were significantly downregulated. The most significantly affected genes C. F. Baptista et al. 106 were as follows: for glycolysis (fold regulation with p < 0.05): Pgm1, Bpgm, Aldob, and Eno3 (119, 45, 18, and 28 times less, respectively); and for the TCA cycle (fold regulation with p < 0.05): Cs, Idh3b, and Mdh2 (84, 27, and 37 times less, respectively). Conclusion: The seven-day leptin treated mice show a decrease in the glucose metabolism. These results confirm the ability of the adipose tissue-derived hormone leptin to regulate early crucial genes that are related to glycolysis mechanisms and to the TCA cycle. This hormone seems to revert early the central physiological conditions that are associated with PCOS; however, the morphological alterations can only be observed within a 45-day treatment.

The present study describes a novel yeast model for the prediction of yeast fermentation. The proposed model considers the possible metabolic pathways of yeast. For each pathway, the time evolution of components, energy (ATP/ADP), and electron carriers (NAD + /NADH) are expressed with limitation factors for all quantities consumed by each respective pathway. In this manner, the model can predict partition of these pathways based on the growth conditions and their evolution over time. Several biological pathways and their stoichiometric coefficients are well-known from literature. It is important to note that most of kinetics parameters have no effect since actual kinetics are controlled by balance of limiting factors. The few remaining parameters were adjusted and compared with the literature when the dataset was available. The model fits our experimental data from yeast fermentation on glucose in non-aerated batch system. The predictive ability of the model and its capacity to represent the intensity of each pathway over time facilitate an improved understanding of interactions between the pathways. The key role of energy (ATP) and electron carrier (NAD +) to trigger the different metabolic pathways during yeast growth is highlighted, while involvement of mitochondrial respiration not being associated with the TCA cycle is also shown.

Aluminum (Al) is an important factor that limits plant growth under acidic soil conditions. However, several plant species developed distinct mechanisms that limit the damage caused by high Al concentrations. In highbush blueberry (Vaccinium corymbosum), the Al resistance mechanisms are not fully understood. This study was designed to evaluate the effect of Al toxicity on roots and leaves of highbush blueberry genotypes with contrasting Al resistance [Star (Al-sensitive) and Camellia and Cargo (Al-resistant)] and identify the main molecular and physiological strategies underpinning adaptive Al stress responses in nutrient solution. After 48 h of the Al treatment, the reduced form of ascorbate (ASC) was higher in roots, but unchanged in leaves of Cargo and Camellia genotypes compared to the control. We also observed decreased root exudation of oxalate in the Al-treated sensitive cultivar Star throughout the treatment period. However, in the resistant cultivar (Camellia), the exudation of oxalate increased 2.4-and 2.8-fold at 24 and 48 h, respectively, compared with t=0. The Al treatment affected differentially the enzyme activity and gene expression of the tricarboxylic acid (TCA) cycle enzymes. The NAD-dependent malate dehydrogenase (NAD-MDH) expression in roots of cultivar Cargo was reduced at 24 h and increased at 48 h, whereas in leaves the expression was higher at 24 h and decreased at 48 h compared to the control. The citrate synthase (CS) activity in Al-resistant Cargo roots diminished at 24 h, increasing afterwards, without variation in the CS gene expression, compared with t=0. In Al-resistant Camellia roots, the gene expression and the activity of CS decreased during Al exposure. NADP-dependent malate dehydrogenase (NADP-MDH) in the leaves of cultivar Cargo showed increased activity and gene expression at 24 h, whereas in roots the gene expression decreased, but the ratio of NADP-MDH initial/final activity increased. The expression of genes encoding enzymes of TCA cycle did not differ significantly in the Al-sensitive cultivar Star during Al exposure. In conclusion, the exudation of organic acid anions, particularly oxalate, plays an important role in Al resistance of highbush blueberry genotypes. In addition, increased concentration of ASC in roots, and a positive correlation between gene expression/enzyme activity of CS and NADP-MDH also contribute to the Al-resistance mechanisms exhibited by genotypes Camellia and Cargo.

Aluminum (Al) is an important factor that limits plant growth under acidic soil conditions. However, several plant species developed distinct mechanisms that limit the damage caused by high Al concentrations. In highbush blueberry (Vaccinium corymbosum), the Al resistance mechanisms are not fully understood. This study was designed to evaluate the effect of Al toxicity on roots and leaves of highbush blueberry genotypes with contrasting Al resistance [Star (Al-sensitive) and Camellia and Cargo (Al-resistant)] and identify the main molecular and physiological strategies underpinning adaptive Al stress responses in nutrient solution. After 48 h of the Al treatment, the reduced form of ascorbate (ASC) was higher in roots, but unchanged in leaves of Cargo and Camellia genotypes compared to the control. We also observed decreased root exudation of oxalate in the Al-treated sensitive cultivar Star throughout the treatment period. However, in the resistant cultivar (Camellia), the exudation of oxalate increased 2.4-and 2.8-fold at 24 and 48 h, respectively, compared with t=0. The Al treatment affected differentially the enzyme activity and gene expression of the tricarboxylic acid (TCA) cycle enzymes. The NAD-dependent malate dehydrogenase (NAD-MDH) expression in roots of cultivar Cargo was reduced at 24 h and increased at 48 h, whereas in leaves the expression was higher at 24 h and decreased at 48 h compared to the control. The citrate synthase (CS) activity in Al-resistant Cargo roots diminished at 24 h, increasing afterwards, without variation in the CS gene expression, compared with t=0. In Al-resistant Camellia roots, the gene expression and the activity of CS decreased during Al exposure. NADP-dependent malate dehydrogenase (NADP-MDH) in the leaves of cultivar Cargo showed increased activity and gene expression at 24 h, whereas in roots the gene expression decreased, but the ratio of NADP-MDH initial/final activity increased. The expression of genes encoding enzymes of TCA cycle did not differ significantly in the Al-sensitive cultivar Star during Al exposure. In conclusion, the exudation of organic acid anions, particularly oxalate, plays an important role in Al resistance of highbush blueberry genotypes. In addition, increased concentration of ASC in roots, and a positive correlation between gene expression/enzyme activity of CS and NADP-MDH also contribute to the Al-resistance mechanisms exhibited by genotypes Camellia and Cargo.

Objective: Effect of oleanolic acid against hexavalent chromium-induced altered brain energy metabolism associated with oxidative stress was evaluated in the present study. Methods: Swiss albino mice were divided into three groups, Control (n=6), chromium-treated (n=6), and oleanolic acid (OA) supplemented (n=6). The chromium treated group was orally administered with K 2 Cr 2 O 7 for 30 days at a dose of 10 mg/kg b.w/day. OA supplementation was given at a dose of 5 mg/kg bw/day for the past 14 days of chromium treatment. Control group received the vehicle only. After the treatment, whole brain was removed for examining the parameters such as pyruvic acid, free amino nitrogen, tissue protein, TCA cycle enzyme activities, NADH dehydrogenase function, and oxidative stress markers. Results: Significant decrease in cerebral pyruvic acid content associated with suppressed malate dehydrogenase and succinate dehydrogenase activities were observed. The NADH dehydrogenase activity was inhibited owing to enhanced accumulation of chromium in cerebral tissue. Depletion of proteins and increased free amino acid nitrogen were accompanied with inhibited cathepsin, pronase and trypsin activities, and increased transaminase function. In addition, GSH content was decreased along with increased lipid peroxidation, oxidized GSSG content, TG/GSSG ratio, carbonylated protein content, and tissue free hydroxyl radical formation. Superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase were also inhibited by hexavalent chromium. Oleanolic acid supplementation was found to have significant protective effect against brain metabolic and oxidative dysfunctions. Conclusion: The present study elucidated therapeutic efficacy of oleanolic acid against hexavalent chromium toxicity in brain tissue of mice.

Plasma levels of branched-chain amino acids (BCAA) are consistently elevated in obesity and type 2 diabetes (T2D) and can also prospectively predict T2D. However, the role of BCAA in the pathogenesis of insulin resistance and T2D remains unclear. To identify pathways related to insulin resistance, we performed comprehensive gene expression and metabolomics analyses in skeletal muscle from 41 humans with normal glucose tolerance and 11 with T2D across a range of insulin sensitivity (SI, 0.49 to 14.28). We studied both cultured cells and mice heterozygous for the BCAA enzyme methylmalonyl-CoA mutase (Mut) and assessed the effects of altered BCAA flux on lipid and glucose homeostasis. Our data demonstrate perturbed BCAA metabolism and fatty acid oxidation in muscle from insulin resistant humans. Experimental alterations in BCAA flux in cultured cells similarly modulate fatty acid oxidation. Mut heterozygosity in mice alters muscle lipid metabolism in vivo, resulting in increased muscle...

High-dose of vitamin C (L-ascorbic acid, ascorbate) exhibits anti-tumoral effects, primarily mediated by pro-oxidant mechanisms. This cytotoxic effect is thought to affect the reciprocal crosstalk between redox balance and cell metabolism in different cancer types. Vitamin C also inhibits the growth of papillary thyroid carcinoma (PTC) cells, although the metabolic and redox effects remain to be fully understood. To shed light on these aspects, PTC-derived cell lines harboring the most common genetic alterations characterizing this tumor were used. Cell viability, apoptosis, and the metabolome were explored by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test (MTT), flow cytometry, and UHPLC/MS. Changes were observed in redox homeostasis, with increased reactive oxygen species (ROS) level and perturbation in antioxidants and electron carriers, leading to cell death by both apoptosis and necrosis. The oxidative stress contributed to the metabolic alterations in both g...

Introduction: Polycystic ovarian syndrome (PCOS) is undoubtedly the commonest androgen disorder in woman's fertile period and certainly one of the most prevalent causes of anovulation. The syndrome has an estimated prevalence of 4%-10% among women of childbearing age. Previously, our group demonstrated the effect of gonadal white adipose tissue transplantation from wild-type lean and fertile female mice to isogenic obese anovulatory ob/ob mice. These complex metabolic interrelationships between obesity and PCOS have yet to be fully understood. The aim of this study was to evaluate the effect of gonadal white adipose tissue (WAT) transplantation from the wildtype lean and fertile female mice to isogenic obese, anovulatory mice (Lep ob/Lep ob) on the expression of glycolysis-and TCA cycle-related genes and obtain a general view of the glucose metabolism in the brain of these animals. Methods: Fifteen ob/ob mice ranging from 2 to 3 months of age were divided into 3 experimental groups: control normal weight (n = 5), obese control (n = 5) and obese 7 days leptin treated (n = 5). The whole brains of the mice were processed for RNA extraction. The samples from each group were used to perform PCR assays using an array plate containing 84 primers to study the glucose metabolism-related genes. Results: The glycolysis-and TCA cycle-related genes were significantly downregulated. The most significantly affected genes C. F. Baptista et al. 106 were as follows: for glycolysis (fold regulation with p < 0.05): Pgm1, Bpgm, Aldob, and Eno3 (119, 45, 18, and 28 times less, respectively); and for the TCA cycle (fold regulation with p < 0.05): Cs, Idh3b, and Mdh2 (84, 27, and 37 times less, respectively). Conclusion: The seven-day leptin treated mice show a decrease in the glucose metabolism. These results confirm the ability of the adipose tissue-derived hormone leptin to regulate early crucial genes that are related to glycolysis mechanisms and to the TCA cycle. This hormone seems to revert early the central physiological conditions that are associated with PCOS; however, the morphological alterations can only be observed within a 45-day treatment.

Cancer is characterized by an uncontrolled cell proliferation rate even under low nutrient availability, which is sustained by a metabolic reprograming now recognized as a hallmark of cancer. Warburg was the first to establish the relationship between cancer and mitochondria; however, he interpreted enhanced aerobic glycolysis as mitochondrial dysfunction. Today it is accepted that many cancer cell types need fully functional mitochondria to maintain their homeostasis. Calcium (Ca 2+)-a key regulator of several cellular processes-has proven to be essential for mitochondrial metabolism. Inositol 1,4,5-trisphosphate receptor (IP3R)-mediated Ca 2+ transfer from the endoplasmic reti culum to the mitochondria through the mitochondrial calcium uniporter (MCU) proves to be essential for the maintenance of mitochondrial function and cellular energy balance. Both IP3R and MCU are overexpressed in several cancer cell types, and the inhibition of the Ca 2+ communication between these two organelles causes proliferation arrest, migration decrease, and cell death through mechanisms that are not fully understood. In this review, we summarize and analyze the current findings in this area, emphasizing the critical role of Ca 2+ and mitochondrial metabolism in cancer and its potential as a novel therapeutic target.

Plant ammonium tolerance has been associated with the capacity to accumulate large amounts of ammonium in the root vacuoles, to maintain carbohydrate synthesis and especially with the capacity of maintaining high levels of inorganic nitrogen assimilation in the roots. The tricarboxylic acid cycle (TCA) is considered a cornerstone in nitrogen metabolism, since it provides carbon skeletons for nitrogen assimilation. The hypothesis of this work was that the induction of anaplerotic routes of phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH) and malic enzyme (NAD-ME) would enhance tolerance to ammonium nutrition. An experiment was established with tomato plants (Agora Hybrid F1) grown under different ammonium concentrations. Growth parameters, metabolite contents and enzymatic activities related to nitrogen and carbon metabolism were determined. Unlike other tomato cultivars, tomato Agora Hybrid F1 proved to be tolerant to ammonium nutrition. Ammonium was assimilated as a biochemical detoxification mechanism, thus leading to the accumulation of Gln and Asn as free amino acids in both leaves and roots as an innocuous and transitory store of nitrogen, in addition to protein synthesis. When the concentration of ammonium in the nutrient solution was high, the cyclic operation of the TCA cycle seemed to be interrupted and would operate in two interconnected branches to provide ␣-ketoglutarate for ammonium assimilation: one branch supported by malate accumulation and by the induction of anaplerotic PEPC and NAD-ME in roots and MDH in leaves, and the other branch supported by stored citrate in the precedent dark period.

4-Hydroxyisoleucine (HIL) found in fenugreek seeds has insulinotropic and anti-obesity effects, and is expected to be a novel orally-active drug for insulin-independent diabetes. Here we show that newly isolated strain Bacillus thuringiensis 2e2 and the closely related strain B. thuringiensis ATCC 35646 operates a novel metabolic pathway for L-isoleucine (L-Ile) via HIL and 2-amino-3-methyl-4-ketopentanoic acid (AMKP). The HIL synthesis was catalyzed stereoselectively by an α-ketoglutaric acid-dependent dioxygenase and to be useful for efficient production of a naturally occurring HIL isomer, (2S,3R,4S)-HIL. The (2S,3R,4S)-HIL was oxidized to (2S,3R)-AMKP by a NAD +-dependent dehydrogenase. The metabolic pathway functions as an effective bypass pathway that compensates for the incomplete TCA cycle in Bacillus species and also explains how AMKP, a vitamin B 12 antimetabolite with antibiotic activity, is synthesized. These novel findings pave a new way for commercial production of HIL and also for AMKP. Keywords L-Isoleucine dioxygenase • 4-Hydroxyisoleucine •NAD +-dependent dehydrogenase • 2-amino-3-methyl-4-ketopentanoic acid • Bacillus thuringiensis • TCA cycle

In response to environmental stimuli, macrophages change their nutrient consumption and undergo an early metabolic adaptation that progressively shapes their polarization state. During the transient, early phase of pro-inflammatory macrophage activation, an increase in tricarboxylic acid (TCA) cycle activity has been reported but the relative contribution of branched chain amino acid (BCAA) leucine remain to be determined. Here we show that glucose but not glutamine is a major contributor of the increase in TCA cycle metabolites during early macrophage activation in humans. We then show that, although BCAA uptake is not altered, their transamination by BCAT1 is increased following 8h lipopolysaccharide (LPS) stimulation. Of note, leucine is not metabolized to integrate the TCA cycle in neither basal nor stimulated human macrophages. Surprisingly, the pharmacological inhibition of BCAT1 reduced glucose-derived itaconate, α-ketoglutarate, and 2-hydroxyglutarate levels, without affecti...

In biological cells, chemical reaction pathways lead to complex network systems like metabolic networks. One experimental approach to the dynamics of such systems examines their &quot;sensitivity&quot;: each enzyme mediating a reaction in the system is increased/decreased or knocked out separately, and the responses in the concentrations of chemicals or their fluxes are observed. In this study, we present a mathematical method, named structural sensitivity analysis, to determine the sensitivity of reaction systems from information on the network alone. We investigate how the sensitivity responses of chemicals in a reaction network depend on the structure of the network, and on the position of the perturbed reaction in the network. We establish and prove some general rules which relate the sensitivity response to the structure of the underlying network. We describe a hierarchical pattern in the flux response which is governed by branchings in the network. We apply our method to sever...

The MSC16 cucumber (Cucumis sativus L.) mitochondrial mutant was used to study the effect of mitochondrial dysfunction and disturbed subcellular redox state on leaf day/night carbon and nitrogen metabolism. We have shown that the mitochondrial dysfunction in MSC16 plants had no effect on photosynthetic CO 2 assimilation, but the concentration of soluble carbohydrates and starch was higher in leaves of MSC16 plants. Impaired mitochondrial respiratory chain activity was associated with the perturbation of mitochondrial TCA cycle manifested, e.g., by lowered decarboxylation rate. Mitochondrial dysfunction in MSC16 plants had different influence on leaf cell metabolism under dark or light conditions. In the dark, when the main mitochondrial function is the energy production, the altered activity of TCA cycle in mutated plants was connected with the accumulation of pyruvate and TCA cycle intermediates (citrate and 2-OG). In the light, when TCA activity is needed for synthesis of carbon skeletons required as the acceptors for NH 4 ? assimilation, the concentration of pyruvate and TCA intermediates was tightly coupled with nitrate metabolism. Enhanced incorporation of ammonium group into amino acids structures in mutated plants has resulted in decreased concentration of organic acids and accumulation of Glu.

The biotechnological production of dicarboxylic acids (C4) from renewable carbon sources represents an attractive approach for the provision of these valuable compounds by green chemistry means. Glycerol has become a waste product of the biodiesel industry that serves as a highly reduced carbon source for some microorganisms. Escherichia coli is capable of consuming glycerol to produce succinate under anaerobic fermentation, but with the deletion of some tricarboxylic acid (TCA) cycle genes, it is also able to produce succinate and malate in aerobiosis. In this study, we investigate possible rate-limiting enzymes by overexpressing the C-feeding anaplerotic enzymes Ppc, MaeA, MaeB, and Pck in a mutant that lacks the succinate dehydrogenase (Sdh) enzyme. The overexpression of the TCA enzyme Mdh and the activation of the glyoxylate shunt was also examined. Using this unbiased approach, we found that phosphoenol pyruvate carboxylase (Ppc) overexpression enhances an oxidative pathway tha...

The biotechnological production of dicarboxylic acids (C4) from renewable carbon sources represents an attractive approach for the provision of these valuable compounds by green chemistry means. Glycerol has become a waste product of the biodiesel industry that serves as a highly reduced carbon source for some microorganisms. Escherichia coli is capable of consuming glycerol to produce succinate under anaerobic fermentation, but with the deletion of some tricarboxylic acid (TCA) cycle genes, it is also able to produce succinate and malate in aerobiosis. In this study, we investigate possible rate-limiting enzymes by overexpressing the C-feeding anaplerotic enzymes Ppc, MaeA, MaeB, and Pck in a mutant that lacks the succinate dehydrogenase (Sdh) enzyme. The overexpression of the TCA enzyme Mdh and the activation of the glyoxylate shunt was also examined. Using this unbiased approach, we found that phosphoenol pyruvate carboxylase (Ppc) overexpression enhances an oxidative pathway tha...

Background: Thyroid cancer is the most common endocrine malignancy, with papillary thyroid carcinoma (PTC) being the most common (85–90%) among all the different types of thyroid carcinomas. Cancer cells show metabolic alterations and, due to their rapid proliferation, an accumulation of reactive oxygen species, playing a fundamental role in cancer development and progression. Currently, the crosstalk among thyrocytes metabolism, redox balance and oncogenic mutations remain poorly characterized. The aim of this study was to investigate the interplay among metabolic alterations, redox homeostasis and oncogenic mutations in PTC-derived cells. Methods: Metabolic and redox profile, glutamate-cysteine ligase, glutaminase-1 and metabolic transporters were evaluated in PTC-derived cell lines with distinguished genetic background (TPC-1, K1 and B-CPAP), as well as in an immortalized thyroid cell line (Nthy-ori3-1) selected as control. Results: PTC-derived cells, particularly B-CPAP cells, h...

Introduction: Polycystic ovarian syndrome (PCOS) is undoubtedly the commonest androgen disorder in woman's fertile period and certainly one of the most prevalent causes of anovulation. The syndrome has an estimated prevalence of 4%-10% among women of childbearing age. Previously, our group demonstrated the effect of gonadal white adipose tissue transplantation from wild-type lean and fertile female mice to isogenic obese anovulatory ob/ob mice. These complex metabolic interrelationships between obesity and PCOS have yet to be fully understood. The aim of this study was to evaluate the effect of gonadal white adipose tissue (WAT) transplantation from the wildtype lean and fertile female mice to isogenic obese, anovulatory mice (Lep ob/Lep ob) on the expression of glycolysis-and TCA cycle-related genes and obtain a general view of the glucose metabolism in the brain of these animals. Methods: Fifteen ob/ob mice ranging from 2 to 3 months of age were divided into 3 experimental groups: control normal weight (n = 5), obese control (n = 5) and obese 7 days leptin treated (n = 5). The whole brains of the mice were processed for RNA extraction. The samples from each group were used to perform PCR assays using an array plate containing 84 primers to study the glucose metabolism-related genes. Results: The glycolysis-and TCA cycle-related genes were significantly downregulated. The most significantly affected genes C. F. Baptista et al. 106 were as follows: for glycolysis (fold regulation with p < 0.05): Pgm1, Bpgm, Aldob, and Eno3 (119, 45, 18, and 28 times less, respectively); and for the TCA cycle (fold regulation with p < 0.05): Cs, Idh3b, and Mdh2 (84, 27, and 37 times less, respectively). Conclusion: The seven-day leptin treated mice show a decrease in the glucose metabolism. These results confirm the ability of the adipose tissue-derived hormone leptin to regulate early crucial genes that are related to glycolysis mechanisms and to the TCA cycle. This hormone seems to revert early the central physiological conditions that are associated with PCOS; however, the morphological alterations can only be observed within a 45-day treatment.

Background: Thyroid cancer is the most common endocrine malignancy, with papillary thyroid carcinoma (PTC) being the most common (85–90%) among all the different types of thyroid carcinomas. Cancer cells show metabolic alterations and, due to their rapid proliferation, an accumulation of reactive oxygen species, playing a fundamental role in cancer development and progression. Currently, the crosstalk among thyrocytes metabolism, redox balance and oncogenic mutations remain poorly characterized. The aim of this study was to investigate the interplay among metabolic alterations, redox homeostasis and oncogenic mutations in PTC-derived cells. Methods: Metabolic and redox profile, glutamate-cysteine ligase, glutaminase-1 and metabolic transporters were evaluated in PTC-derived cell lines with distinguished genetic background (TPC-1, K1 and B-CPAP), as well as in an immortalized thyroid cell line (Nthy-ori3-1) selected as control. Results: PTC-derived cells, particularly B-CPAP cells, h...

In Aspergillus nidulans, the utilization of acetate as sole carbon source requires several genes (acu). Most of 31 them are also required for the utilization of fatty acids. This is the case for acuD and acuE, which encode 32 the two glyoxylate cycle-specific enzymes, isocitrate lyase and malate synthase, respectively, but also for 33 acuL that we have identified as AN7287, and characterized in this study. Deletion of acuL resulted in the 34 same phenotype as the original acuL217 mutant. acuL encodes a 322-amino acid protein which displays 35 all the structural features of a mitochondrial membrane carrier, and shares 60% identity with the 36 Saccharomyces cerevisiae succinate/fumarate mitochondrial antiporter Sfc1p (also named Acr1p). 37 Consistently, the AcuL protein was shown to localize in mitochondria, and partial cross-complementation 38 was observed between the S. cerevisiae and A. nidulans homologues. Extensive phenotypic characteriza-39 tion suggested that the acuL gene is involved in the utilization of carbon sources that are catabolized 40 via the TCA cycle, and therefore require gluconeogenesis. In addition, acuL proves to be co-regulated with 41 acuD and acuE. Overall, our data suggest that AcuL could link the glyoxylate cycle to gluconeogenesis by 42 exchanging cytoplasmic succinate for mitochondrial fumarate.

We investigated the effects of the expression of the Escherichia coli ppc gene encoding PEP carboxylase in Saccharomyces cerevisiae mutants devoid of pyruvate carboxylase. Functional expression of the ppc gene restored the ability of the yeast mutants to grow in glucose-ammonium medium. Growth yield in this medium was the same in the transformed yeast than in the wild type although the growth rate of the transformed yeast was slower. Growth in pyruvate was slowed down in the transformed strain, likely due to a futile cycle produced by the simultaneous action of PEP carboxykinase and PEP carboxylase.

Plant ammonium tolerance has been associated with the capacity to accumulate large amounts of ammonium in the root vacuoles, to maintain carbohydrate synthesis and especially with the capacity of maintaining high levels of inorganic nitrogen assimilation in the roots. The tricarboxylic acid cycle (TCA) is considered a cornerstone in nitrogen metabolism, since it provides carbon skeletons for nitrogen assimilation. The hypothesis of this work was that the induction of anaplerotic routes of phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH) and malic enzyme (NAD-ME) would enhance tolerance to ammonium nutrition. An experiment was established with tomato plants (Agora Hybrid F1) grown under different ammonium concentrations. Growth parameters, metabolite contents and enzymatic activities related to nitrogen and carbon metabolism were determined. Unlike other tomato cultivars, tomato Agora Hybrid F1 proved to be tolerant to ammonium nutrition. Ammonium was assimilated as a biochemical detoxification mechanism, thus leading to the accumulation of Gln and Asn as free amino acids in both leaves and roots as an innocuous and transitory store of nitrogen, in addition to protein synthesis. When the concentration of ammonium in the nutrient solution was high, the cyclic operation of the TCA cycle seemed to be interrupted and would operate in two interconnected branches to provide ␣-ketoglutarate for ammonium assimilation: one branch supported by malate accumulation and by the induction of anaplerotic PEPC and NAD-ME in roots and MDH in leaves, and the other branch supported by stored citrate in the precedent dark period.

Mitochondria have been implicated in the ageing process and the lifespan modulation of model organisms. Mitochondria are the main providers of energy in eukaryotic cells but also represent both a major source of reactive oxygen species and targets for protein oxidative damage. Since protein damage can impair mitochondrial function, mitochondrial proteases are critically important for protein maintenance and elimination of oxidized protein. In the mitochondrial matrix, protein quality control is mainly achieved by the Lon and Clp proteases which are also key players in damaged mitochondrial proteins degradation. Accumulation of damaged macromolecules resulting from oxidative stress and failure of protein maintenance constitutes a hallmark of cellular and organismal ageing and is believed to participate to the age-related decline of cellular function. Hence, age-related impairment of mitochondrial protein quality control may therefore contribute to the age-associated build-up of oxidized protein and alterations of mitochondrial redox and protein homeostasis.

The forest ecosystem is of particular importance from an economic and ecological perspective. However, the stress physiology of trees, perennial and woody plants, is far from being fully understood. For that purpose, poplar plants were exposed to drought; the plants exhibited commonly reported drought stress traits in the different plant tissues. Leafy rooted cuttings of poplar were investigated through a proteomic approach in order to compare the water constraint response of two plant tissues, namely leaf and cambium. Sampling was realized during the drought period at 2 time points with increased drought intensity and 7 days after rewatering. Our data show that there is a difference in the moment of response to the water constraint between the two tissues, cambium being affected later than leaves. In leaves, drought induced a decrease in rubisco content, and an increase in the abundance of light harvesting complex proteins as well as changes in membrane-related proteins. In the cambial tissue, the salient proteome pattern change was the decrease of multiple proteins identified as bark storage proteins. After rewatering, almost all changes in cambial proteome disappeared whereas a significant number of leaf proteins appeared to be differentially regulated only during the recovery from drought.

Reperfusion of ischemic tissue leads to the generation of oxygen derived free radicals which plays an important role in cellular damage. Objective of the current study is to evaluate the cardio-protective and antioxidant effect of diosmin on ischemia-reperfusion related cardiac dysfunction, oxidative stress and apoptosis. Diosmin (50 and 100 mg/kg body weight (bw)) was given every day to the rats orally throughout the experimental period. Ischemia/reperfusion protocol was carried out ex vivo using langendorff perfusion method and the cardiac functional recovery was assessed in terms of percentage rate pressure product. Coronary effluents of LDH and CK-MB activities, antioxidant enzyme activities, lipid peroxidation products, activity of TCA cycle enzymes were evaluated. Moreover, in vitro superoxide anion and hydroxyl radical scavenging potential of diosmin was also quantified. Finally, quantitative realtime PCR was used for assessing Bcl-2 mRNA expression in heart. Cardiac functional recovery was impaired after reperfusion compared with continuously perfused heart. It was significantly prevented by diosmin treatment. Impaired antioxidant enzyme activities and elevated lipid peroxidation products level were also significantly suppressed. The activity of TCA cycle enzymes was protected against reperfusion stress. Down regulated Bcl-2 was also significantly increased. This study concluded that diosmin pretreatment prevents all the impaired patterns including cardiac function, oxidative stress and apoptosis associated with reperfusion in control heart by its antioxidant role.

Transgenic tomato (Solanum lycopersicum) plants were generated targeting the cytosolic NADPdependent isocitrate dehydrogenase gene (SlICDH1) via the RNA interference approach. The resultant transformants displayed a relatively mild reduction in the expression and activity of the target enzyme in the leaves. However, biochemical analyses revealed that the transgenic lines displayed a considerable shift in metabolism, being characterized by decreases in the levels of the TCA cycle intermediates, total amino acids, photosynthetic pigments, starch and NAD(P)H. The plants showed little change in photosynthesis with the exception of a minor decrease in maximum photosynthetic efficiency (F v /F m), and a small decrease in growth compared to the wild type. These results reveal that even small changes in cytosolic NADP-dependent isocitrate dehydrogenase activity lead to noticeable alterations in the activities of enzymes involved in primary nitrate assimilation and in the synthesis of 2oxoglutarate derived amino acids. These data are discussed within the context of current models for the role of the various isoforms of isocitrate dehydrogenase within plant amino acid metabolism. Keywords Cytosolic isocitrate dehydrogenase Á Solanum lycopersicum Á Mitochondria Á TCA cycle Á Nitrogen metabolism Á Amino acid biosynthesis

4-Hydroxyisoleucine (HIL) found in fenugreek seeds has insulinotropic and anti-obesity effects, and is expected to be a novel orally-active drug for insulin-independent diabetes. Here we show that newly isolated strain Bacillus thuringiensis 2e2 and the closely related strain B. thuringiensis ATCC 35646 operates a novel metabolic pathway for L-isoleucine (L-Ile) via HIL and 2-amino-3-methyl-4-ketopentanoic acid (AMKP). The HIL synthesis was catalyzed stereoselectively by an α-ketoglutaric acid-dependent dioxygenase and to be useful for efficient production of a naturally occurring HIL isomer, (2S,3R,4S)-HIL. The (2S,3R,4S)-HIL was oxidized to (2S,3R)-AMKP by a NAD + -dependent dehydrogenase. The metabolic pathway functions as an effective by-pass pathway that compensates for the incomplete TCA cycle in Bacillus species and also explains how AMKP, a vitamin B 12 antimetabolite with antibiotic activity, is synthesized. These novel findings pave a new way for commercial production of HIL and also for AMKP. Keywords L-Isoleucine dioxygenase • 4-Hydroxyisoleucine •NAD + -dependent dehydrogenase • 2-amino-3-methyl-4-ketopentanoic acid • Bacillus thuringiensis • TCA cycle

ÐThe role of the tricarboxylic (TCA) cycle and the glyoxylate pathway in anaerobic accumulation of poly-b-hydroxyalkanoates by enhanced biological phosphorus removal (EBPR) activated sludge was investigated. Accumulation of both poly-b-hydroxybutyrate (PHB) and poly-bhydroxyvalerate (PHV) was observed, after feeding acetate to fresh activated sludge collected from a pilot-scale EBPR facility. Based on the supplied amount of carbon nutrient the level of PHA synthesis exceeded the level of expected synthesis. Feeding of pyruvate combined with acetate resulted in accumulation of PHB and PHV, in approximately a 1:1 ratio. Citrate addition did not result in PHA accumulation but both PHB and PHV were formed when citrate combined with acetate was fed to the sludge. Succinate or succinate combined with acetate stimulated 2-fold higher accumulation of PHV than PHB. In most cases of synthesis, total PHA accumulation exceeded total carbon input. This excess accumulation suggests the presence of nutrients that are normally unusable or cryptic in the absence of additional complementary nutrients such as short chain fatty acids. This hypothesis is consistent with the fragmentation patterns produced during gas chromatography-mass spectrometric (GC/MS) analyses of PHA extracted from sludge fed with 13 C-labeled nutrients. Treating the EBPR sludge by adding dierent nutrients combined with malonate, a-ketoglutarate and mono¯uoroacetate, three common inhibitors of steps in the TCA cycle signi®cantly impaired PHA accumulation and implied that these steps can be important for PHA synthesis. A biochemical model that incorporates elements of the TCA cycle and the glyoxylate pathway can account for the observed patterns of PHA accumulation.