6-Phosphogluconolactonase (6PGL) is one of the key enzymes in the ubiquitous pathways of central carbon metabolism, but bacterial 6PGL had been long known as a missing enzyme even after complete bacterial genome sequence information became available. Although recent experimental characterization suggests that there are two types of 6PGLs (DevB and YbhE), their phylogenetic distribution is severely biased. Here we present that proteins in COG group previously described as 3-carboxymuconate cyclase (COG2706) are actually the YbhE-type 6PGLs, which are widely distributed in Proteobacteria and Firmicutes. This case exemplifies how erroneous functional description of a member in the reference database commonly used in transitive genome annotation cause systematic problem in the prediction of genes even with universal cellular functions.
Bias (Epidemiology) ; Carbon ; Computer Simulation* ; Genome ; Genome, Bacterial* ; Metabolism ; Pentose Phosphate Pathway ; Proteobacteria

Energy metabolism is significantly reprogrammed in many human cancers, and these alterations confer many advantages to cancer cells, including the promotion of biosynthesis, ATP generation, detoxification and support of rapid proliferation. The pentose phosphate pathway (PPP) is a major pathway for glucose catabolism. The PPP directs glucose flux to its oxidative branch and produces a reduced form of nicotinamide adenine dinucleotide phosphate (NADPH), an essential reductant in anabolic processes. It has become clear that the PPP plays a critical role in regulating cancer cell growth by supplying cells with not only ribose-5-phosphate but also NADPH for detoxification of intracellular reactive oxygen species, reductive biosynthesis and ribose biogenesis. Thus, alteration of the PPP contributes directly to cell proliferation, survival and senescence. Furthermore, recent studies have shown that the PPP is regulated oncogenically and/or metabolically by numerous factors, including tumor suppressors, oncoproteins and intracellular metabolites. Dysregulation of PPP flux dramatically impacts cancer growth and survival. Therefore, a better understanding of how the PPP is reprogrammed and the mechanism underlying the balance between glycolysis and PPP flux in cancer will be valuable in developing therapeutic strategies targeting this pathway.
Animals ; Energy Metabolism ; Glucose ; metabolism ; Glycolysis ; Humans ; Neoplasms ; metabolism ; pathology ; Pentose Phosphate Pathway ; physiology

OBJECTIVE: Previously, we identified that transketolase (Tkt), an important enzyme in the pentose phosphate pathway, is highly expressed at 2 hours of spontaneous maturation in oocytes. Therefore, this study was performed to determine the function of Tkt in meiotic cell cycle regulation, especially at the point of germinal vesicle breakdown (GVBD). METHODS: We evaluated the loss-of-function of Tkt by microinjecting Tkt double-stranded RNAs (dsRNAs) into germinal vesicle-stage oocytes, and the oocytes were cultured in vitro to evaluate phenotypic changes during oocyte maturation. In addition to maturation rates, meiotic spindle and chromosome rearrangements, and changes in expression of other enzymes in the pentose phosphate pathway were determined after Tkt RNA interference (RNAi). RESULTS: Despite the complete and specific knockdown of Tkt expression, GVBD occurred and meiosis was arrested at the metaphase I (MI) stage. The arrested oocytes exhibited spindle loss, chromosomal aggregation, and declined maturation promoting factor and mitogen-activated protein kinase activities. The modified expression of two enzymes in the pentose phosphate pathway, Prps1 and Rbks, after Tkt RNAi and decreased maturation rates were amended when ribose-5-phosphate was supplemented in the culture medium, suggesting that the Tkt and pentose phosphate pathway are important for the maturation process. CONCLUSION: We concluded that Tkt and its associated pentose phosphate pathway play an important role in the MI-MII transition of the oocytes' meiotic cell cycle, but not in the process of GVBD.
Cell Cycle ; Maturation-Promoting Factor ; Meiosis ; Metaphase ; Oocytes ; Pentose Phosphate Pathway ; Protein Kinases ; Ribosemonophosphates ; RNA Interference ; RNA, Double-Stranded ; Transketolase

Glucose-6-phosphate dehydrogenase (G6PDH) catalyzes the first and rate-limiting step of the oxidative pentose phosphate pathway, existing in both cytosolic and plastidic compartments of higher plants. Its main function is to provide reducing power (NADPH) and pentose phosphates for reductive biosynthesis and maintenance of the redox state of the cell. In addition, the expression of this enzyme is related to different biotic and abiotic stresses. In this review, we analyzed the isoenzyme, regulation and biological function of G6PDH. Meanwhile, we summarized the progress work of G6PDH involved in stress resistance, gene cloning, enzyme-deficiency and cluster analysis. Problems should be solved were also discussed.
Amino Acid Sequence ; Glucosephosphate Dehydrogenase ; genetics ; metabolism ; physiology ; Isoenzymes ; Molecular Sequence Data ; Pentose Phosphate Pathway ; physiology ; Plants ; enzymology ; metabolism

OBJECTIVE: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect. G6PD plays a key role in the pentose phosphate pathway, which is a major source of nicotinamide adenine dinucleotide phosphate (NADPH). NADPH provides the reducing equivalents for oxidation-reduction reductions involved in protecting against the toxicity of reactive oxygen species such as H₂O₂. We hypothesized that G6PD deficiency may reduce the amount of NADPH in sperms, thereby inhibiting the detoxification of H₂O₂, which could potentially affect their motility and viability, resulting in an increased susceptibility to infertility. METHODS: Semen samples were obtained from four males with G6PD deficiency and eight healthy males as a control. In both groups, motile sperms were isolated from the seminal fluid and incubated with 0, 10, 20, 40, 60, 80, and 120 µM concentrations of H2O2. After 1 hour incubation at 37℃, sperms were evaluated for motility and viability. RESULTS: Incubation of sperms with 10 and 20 µM H₂O₂ led to very little decrease in motility and viability, but motility decreased notably in both groups in 40, 60, and 80 µM H₂O₂, and viability decreased in both groups in 40, 60, 80, and 120 µM H₂O₂. However, no statistically significant differences were found between the G6PD-deficient group and controls. CONCLUSION: G6PD deficiency does not increase the susceptibility of sperm to oxidative stress induced by H₂O₂, and the reducing equivalents necessary for protection against H₂O₂ are most likely produced by other pathways. Therefore, G6PD deficiency cannot be considered as major risk factor for male infertility.
Glucose-6-Phosphate* ; Glucosephosphate Dehydrogenase Deficiency* ; Glucosephosphate Dehydrogenase* ; Humans ; Infertility ; Infertility, Male ; Male ; NADP ; Oxidation-Reduction ; Oxidative Stress* ; Pentose Phosphate Pathway ; Reactive Oxygen Species ; Risk Factors ; Semen ; Spermatozoa*

OBJECTIVETo investigate the effect of blood glucose instability on respiratory burst of leukocytes in patients with type 2 diabetes (T2DM).

METHODSForty-five patients with T2DM were divided into 3 groups after continuous glucose monitoring for 72 h with glucose wavy coefficient <1.5 (n=11), between 1.5 and 3.0 (n=19), and >3.0 (n=15). Peripheral blood neutrophils were isolated from the diabetic patients and normal control subjects for assay of glucose 6-phosphate dehydrogenase (G6PD) with a spectrophotometric method, detecting G6PD mRNA expression by real-time PCR, and determining reactive oxygen species level using the fluorescent probe DCFH-DA.

RESULTSCompared with the normal control group, the diabetic patients showed significantly lowered G6PD activity (F=78.739, P<0.05) and ROS level (F=384.962, P<0.05) but significantly increased G6PD mRNA expression (F=269.612, P<0.01). These changes were significantly correlated with the blood glucose wavy coefficients.

CONCLUSIONThe fluctuation of blood glucose in T2DM patients can decrease G6PD activity and lead to functional decline of the respiratory burst.

Blood Glucose ; chemistry ; Case-Control Studies ; Diabetes Mellitus, Type 2 ; metabolism ; Glucosephosphate Dehydrogenase ; metabolism ; Humans ; Neutrophils ; metabolism ; Pentose Phosphate Pathway ; Reactive Oxygen Species ; metabolism ; Respiratory Burst

During cancer progression, cancer cells are repeatedly exposed to metabolic stress conditions in a resource-limited environment which they must escape. Increasing evidence indicates the importance of nicotinamide adenine dinucleotide phosphate (NADPH) homeostasis in the survival of cancer cells under metabolic stress conditions, such as metabolic resource limitation and therapeutic intervention. NADPH is essential for scavenging of reactive oxygen species (ROS) mainly derived from oxidative phosphorylation required for ATP generation. Thus, metabolic reprogramming of NADPH homeostasis is an important step in cancer progression as well as in combinational therapeutic approaches. In mammalian, the pentose phosphate pathway (PPP) and one-carbon metabolism are major sources of NADPH production. In this review, we focus on the importance of glucose flux control towards PPP regulated by oncogenic pathways and the potential therein for metabolic targeting as a cancer therapy. We also summarize the role of Snail (Snai1), an important regulator of the epithelial mesenchymal transition (EMT), in controlling glucose flux towards PPP and thus potentiating cancer cell survival under oxidative and metabolic stress.
Adenosine Triphosphate ; Cell Survival ; Epithelial-Mesenchymal Transition ; Glucose ; Glucosephosphate Dehydrogenase ; Homeostasis ; Metabolism ; NADP ; Oxidative Phosphorylation ; Pentose Phosphate Pathway ; Reactive Oxygen Species ; Snails ; Stress, Physiological ; United Nations

Despite overall reductions in heart disease prevalence, the risk of developing heart failure has remained 2-fold greater among people with diabetes. Growing evidence has supported that fluctuations in glucose level and uptake contribute to cardiovascular disease (CVD) by modifying proteins, DNA, and gene expression. In the case of glucose, clinical studies have shown that increased dietary sugars for healthy individuals or poor glycemic control in diabetic patients further increased CVD risk. Furthermore, even after decades of maintaining tight glycemic control, susceptibility to disease progression can persist following a period of poor glycemic control through a process termed "glycemic memory." In response to chronically elevated glucose levels, a number of studies have identified molecular targets of the glucose-mediated protein posttranslational modification by the addition of an O-linked N-acetylglucosamine to impair contractility, calcium sensitivity, and mitochondrial protein function. Additionally, elevated glucose contributes to dysfunction in coupling glycolysis to glucose oxidation, pentose phosphate pathway, and polyol pathway. Therefore, in the "sweetened" environment associated with hyperglycemia, there are a number of pathways contributing to increased susceptibly to "breaking" the heart of diabetics. In this review we will discuss the unique contribution of glucose to heart disease and recent advances in defining mechanisms of action.
Calcium ; Cardiomyopathies ; Cardiovascular Diseases ; Diabetic Cardiomyopathies* ; Dietary Sucrose ; Disease Progression ; DNA ; Gene Expression ; Glucose* ; Glycolysis ; Heart ; Heart Diseases ; Heart Failure ; Humans ; Hyperglycemia ; Metabolism ; Mitochondrial Proteins ; Pentose Phosphate Pathway ; Prevalence ; Protein Processing, Post-Translational

A large amount of nicotinamide adenine dinucleotide phosphate (NADPH) is required for fatty acid synthesis and maintenance of the redox state in cancer cells. Malic enzyme 1(ME1)-dependent NADPH production is one of the three pathways that contribute to the formation of the cytosolic NADPH pool. ME1 is generally considered to be overexpressed in cancer cells to meet the high demand for increased de novo fatty acid synthesis. In the present study, we found that glucose induced higher ME1 activity and that repressing ME1 had a profound impact on glucose metabolism of nasopharyngeal carcinoma(NPC) cells. High incorporation of glucose and an enhancement of the pentose phosphate pathway were observed in ME1-repressed cells. However, there were no obvious changes in the other two pathways for glucose metabolism: glycolysis and oxidative phosphorylation. Interestingly, NADPH was decreased under low-glucose condition in ME1-repressed cells relative to wild-type cells, whereas no significant difference was observed under high-glucose condition. ME1-repressed cells had significantly decreased tolerance to low-glucose condition. Moreover, NADPH produced by ME1 was not only important for fatty acid synthesis but also essential for maintenance of the intracellular redox state and the protection of cells from oxidative stress. Furthermore, diminished migration and invasion were observed in ME1-repressed cells due to a reduced level of Snail protein. Collectively, these results suggest an essential role for ME1 in the production of cytosolic NADPH and maintenance of migratory and invasive abilities of NPC cells.
Carcinoma ; Cell Line, Tumor ; Cell Movement ; Cell Survival ; Glucose ; metabolism ; Glycolysis ; Humans ; Malate Dehydrogenase ; metabolism ; NADP ; metabolism ; Nasopharyngeal Neoplasms ; metabolism ; pathology ; Neoplasm Invasiveness ; Oxidation-Reduction ; Oxidative Phosphorylation ; Pentose Phosphate Pathway ; Proto-Oncogene Proteins c-akt ; metabolism

PURPOSE: Obesity is associated with metabolic dysregulation, but the underlying metabolic signatures involving clinical and inflammatory profiles of obese asthma are largely unexplored. We aimed at identifying the metabolic signatures of obese asthma. METHODS: Eligible subjects with obese (n = 11) and lean (n = 22) asthma underwent body composition and clinical assessment, sputum induction, and blood sampling. Sputum supernatant was assessed for interleukin (IL)-1β, -4, -5, -6, -13, and tumor necrosis factor (TNF)-α, and serum was detected for leptin, adiponectin and C-reactive protein. Untargeted gas chromatography time-of-flight mass spectrometry (GC-TOF-MS)-based metabolic profiles in sputum, serum and peripheral blood monocular cells (PBMCs) were analyzed by orthogonal projections to latent structures-discriminate analysis (OPLS-DA) and pathway topology enrichment analysis. The differential metabolites were further validated by correlation analysis with body composition, and clinical and inflammatory profiles. RESULTS: Body composition, asthma control, and the levels of IL-1β, -4, -13, leptin and adiponectin in obese asthmatics were significantly different from those in lean asthmatics. OPLS-DA analysis revealed 28 differential metabolites that distinguished obese from lean asthmatic subjects. The validation analysis identified 18 potential metabolic signatures (11 in sputum, 4 in serum and 2 in PBMCs) of obese asthmatics. Pathway topology enrichment analysis revealed that cyanoamino acid metabolism, caffeine metabolism, alanine, aspartate and glutamate metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, pentose phosphate pathway in sputum, and glyoxylate and dicarboxylate metabolism, glycerolipid metabolism and pentose phosphate pathway in serum are suggested to be significant pathways related to obese asthma. CONCLUSIONS: GC-TOF-MS-based metabolomics indicates obese asthma is characterized by a metabolic profile different from lean asthma. The potential metabolic signatures indicated novel immune-metabolic mechanisms in obese asthma with providing more phenotypic and therapeutic implications, which needs further replication and validation.
Adiponectin ; Alanine ; Aspartic Acid ; Asthma* ; Body Composition ; C-Reactive Protein ; Caffeine ; Chromatography, Gas ; Glutamic Acid ; Interleukins ; Leptin ; Mass Spectrometry ; Metabolism ; Metabolome ; Metabolomics ; Obesity ; Pentose Phosphate Pathway ; Phenylalanine ; Pilot Projects* ; Sputum ; Tryptophan ; Tumor Necrosis Factor-alpha ; Tyrosine