Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Deficient activity of an enzyme can result from a defect in the conversion of the vitamin to a co-enzyme as well from an abnormal apo-enzyme or disturbed binding of coenzyme to enzyme. Conversion of dietary vitamin to intracellular active co-enzyme can be complex and require many physiological and biochemical processes including stomach release of bound vitamin, intestinal uptake, carriers/transport, blood transport, cellular uptake, intracellular release and intracellular compartmentalisation. Disorders of malabsorption (food cobalamin malabsorption, intrinsic factor deficiency and abnormal enterocyte cobalamin processing) and transport proteins (transcobalamin II deficiency, R-binder deficiency) mostly lead to disturbed function of the two cobalamin requiring enzymes, methylmalonyl CoA mutase and methionine synthase. Defects of early steps of intracellular cobalamin (cblF, cbl C/D) result in marked deficiencies of both cobalamin co-enzymes and homocystinuria combined with methylmalonic aciduria. Defective synthesis of adenosyl cobalamin in the cbl A/B defects leads to methylmalonyl CoA mutase. Isolated methionine synthase deficiency is also classified as a cobalamin disorder due to its associated deficient formation of methylcobalamin. Folate disorders include methylene-tetrahydrofolate reductase deficiency and glutamate formimino-transferase deficiency. In addition a hereditary disorder of intestinal folate transport has been described. Less well established are disorders of dihydrofolate reductase, methenyl-tetrahydrofolate cyclohydrolase, and defects of cellular folate uptake.
 ...
PMID:Genetic defects of folate and cobalamin metabolism. 958 28

The role of mitochondrial energy metabolism in glutamate mediated neurotoxicity was studied in rat neurones in primary culture. A brief (15 min) exposure of the neurones to glutamate caused a dose-dependent (0.01-1 mM) increase in cyclic GMP levels together with delayed (24 h) neurotoxicity and ATP depletion. These effects were prevented by either the nitric oxide (.NO) synthase (NOS) inhibitor Nomega-nitro-L-arginine methyl ester (NAME; 1 mM) or by the N-methyl-D-aspartate (NMDA) glutamate-subtype receptor antagonist D-(-)-2-amino-5-phosphonopentanoate (APV; 0.1 mM). Glutamate exposure (0.1 mM and 1 mM) followed by 24 h of incubation caused the inhibition of succinate-cytochrome c reductase (20-25%) and cytochrome c oxidase (31%) activities in the surviving neurones, without affecting NADH-coenzyme-Q1 reductase activity. The rate of oxygen consumption was impaired in neurones exposed to 1 mM glutamate, either with glucose (by 26%) or succinate (by 39%) as substrates. These effects on the mitochondrial respiratory chain and neuronal respiration, together with the observed glutathione depletion (20%) by glutamate exposure were completely prevented by NAME or APV. Our results suggest that mitochondrial dysfunction and impairment of antioxidant status may account for glutamate-mediated neurotoxicity via a mechanism involving .NO biosynthesis.
 ...
PMID:Glutamate neurotoxicity is associated with nitric oxide-mediated mitochondrial dysfunction and glutathione depletion. 959 99

We engineered an expression unit composed of three eukaryotic genes driven by a single plant-active promoter and demonstrated functional expression in planta. The individual genes were linked as translational fusions to produce a polyprotein using spacer sequences encoding specific heptapeptide cleavage recognition sites for NIa protease of tobacco vein mottling virus (TVMV). The NIa gene itself was included as the second gene of the multi-gene unit. The first and third genes, obtained from the TR region of pTi15955, encoded enzymatic functions associated with the mannityl opine biosynthetic pathway. The mannityl opine conjugase gene (mas2) was the first unit of the construct and provided the native plant-active promoter and 5' untranslated regulatory sequence. The third gene (mas1), encoding the mannityl opine reductase, furnished the native 3' untranslated region. Cis-processing of the polyprotein by the NIa protease domain was demonstrated in vitro using rabbit reticulocyte lysate and wheat germ cell-free translation systems. Tobacco plant cells transformed with the multi-gene unit produced detectable levels of mannopine, mannopinic acid, and their biosynthetic intermediates, deoxyfructosyl-glutamate and deoxyfructosyl-glutamine. This indicates that the polygene construct results in a set of functional enzymatic activities that constitute a complete metabolic pathway.
 ...
PMID:Expression of multiple eukaryotic genes from a single promoter in Nicotiana. 963 98

To examine the effect of endurance training (6 wk of treadmill running) on regional mitochondrial adaptations within skeletal muscle, subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria were isolated from trained and control rat hindlimb muscles. Mitochondrial oxygen consumption (VO2) was measured polarographically by using the following substrates: 1 mM pyruvate + 1 mM malate (P+M), 10 mM 2-oxoglutarate, 45 microM palmitoyl-DL-carnitine + 1 mM malate, and 10 mM glutamate. Spectrophotometric assays of cytochrome-c reductase and NAD-specific isocitrate dehydrogenase (IDH) activity were also performed. Maximal (state III) and resting (state IV) VO2 were lower in SS than in IMF mitochondria in both trained and control groups. In SS mitochondria, training elicited significant 36 and 20% increases in state III VO2 with P+M and glutamate, respectively. In IMF mitochondria, training resulted in a smaller (20%), yet significant, increase in state III VO2 with P+M as a substrate, whereas state III VO2 increased 33 and 27% with 2-oxoglutarate and palmitoyl-DL-carnitine + malate, respectively. Within groups, cytochrome-c reductase and IDH activities were lower in SS when compared with IMF mitochondria. Training increased succinate-cytochrome-c reductase in both SS (30%) and IMF mitochondria (28%). IDH activity increased 32% in the trained IMF but remained unchanged in SS mitochondria. We conclude that endurance training promotes substantial changes in protein stoichiometry and composition of both SS and IMF mitochondria.
 ...
PMID:Differential responses to endurance training in subsarcolemmal and intermyofibrillar mitochondria. 976 Mar 17

The mixed culture system was considered in the present research where sugars such as glucose were converted to lactate by Lactobacillus delbrueckii and the lactate was converted to poly beta-hydroxybutyrate (PHB) by Alcaligenes eutrophus in one fermentor. For the modeling of the effect of NH3 concentration on the cell growth of A. eutrophus and PHB production rates, metabolic flux distributions were computed at two culture phases of cell growth and PHB production periods. It was found that the NADPH, generated through isocitrate dehydrogenate in TCA cycle, was predominantly utilized for the reaction from alpha-ketoglutalate to glutamate when NH3 was abundant, while it tended to be utilized for the PHB production through acetoacetyl CoA reductase as NH3 concentration decreased. This phenomenon was reflected in the development of mathematical model. In the mixed culture experiments, the two phases were observed, namely the lactate production phase due to L. delbrueckii and the lactate consumption phase due to A. eutrophus. The lactate concentration could be estimated on-line by the amount of NaOH solution and HCl solution supplied to keep the culture pH at constant level. Several mixed culture experiments were conducted to see the dynamics of the system. Finally, a mathematical model which can describe the dynamic behavior of the present mixed culture was developed and the model parameters were tuned for fitting the experimental data. The model may be used for several purposes such as control, optimization, and understanding process dynamics etc.
 ...
PMID:Dynamics and modeling on fermentative production of poly (beta-hydroxybutyric acid) from sugars via lactate by a mixed culture of Lactobacillus delbrueckii and Alcaligenes eutrophus. 999 Jul 31

Clostridium sticklandii utilizes combinations of amino acids for growth by Stickland reactions. Proline is an efficient electron acceptor in these reactions and is reduced to 5-aminovalerate. Proline can be partly synthesized from ornithine by the action of ornithine aminotransferase and delta1-pyrroline-5-carboxylate (PCA) reductase. Both enzymes were present in crude extracts of C. sticklandii in sufficient activity of 0.93 nkat (mg protein)(-1) and 4.3 nkat (mg protein)(-1), respectively, whereas enzymes involved in proline biosynthesis from glutamate were not detected. PCA reductase was purified to homogeneity in a three-step procedure involving ammonium sulfate precipitation, affinity chromatography with Procion Red and gel filtration on Sephadex GF200. The homogeneous enzyme was most likely an octamer of 230 kDa with a subunit size of 25 kDa as obtained by SDS-PAGE and 28.9 kDa as calculated from the sequence. Apparent Km values for PCA and NADH were 0.19 mM and 0.025 mM, respectively. The enzyme also catalysed in vitro the reverse reaction, the oxidation of proline, at alkaline pH values above 8 and higher substrate concentrations (apparent Km values: 1.55 mM for proline and 10.5 mM for NAD at pH 10.0). Studies with growing cells of C. sticklandii and [15N]proline revealed that proline is not oxidized in vivo because 15N was solely detected by HPLC-MS in 5-aminovalerate as the product of proline reduction. The proC gene encoding PCA reductase of C. sticklandii was cloned, sequenced and heterologously expressed in Escherichia coli. The enzyme exhibited high homologies to PCA reductases from different sources. Thus, C. sticklandii is able to synthesize the electron acceptor proline from ornithine (a degradation product of arginine) by action of ornithine aminotransferase and PCA reductase.
 ...
PMID:Proline biosynthesis from L-ornithine in Clostridium sticklandii: purification of delta1-pyrroline-5-carboxylate reductase, and sequence and expression of the encoding gene, proC. 1022 Jan 61

Mycothione reductase from the human pathogen Mycobacterium tuberculosis has been cloned, expressed in Mycobacterium smegmatis, and purified 145-fold to homogeneity in 43% yield. Amino acid sequence alignment of mycothione reductase with the functionally homologous glutathione and trypanothione reductase indicates conservation of the catalytically important redox-active disulfide, histidine-glutamate ion pair, and regions involved in binding both the FAD cofactor and the substrate NADPH. The homogeneous 50 kDa subunit enzyme exists as a homodimer and is NADPH-dependent and highly specific for the structurally unique low-molecular mass disulfide, mycothione, exhibiting Michaelis constants of 8 and 73 microM for NADPH and mycothione, respectively. HPLC analysis indicated the presence of 1 mol of bound FAD per monomer as the cofactor exhibiting an absorption spectrum with a lambda(max) at 462 nm with an extinction coefficient of 11 300 M(-)(1) cm(-)(1). The reductive titration of the enzyme with NADH indicates the presence of a charge-transfer complex of one of the presumptive catalytic thiolates and FAD absorbing at ca. 530 nm. Reaction with serially truncated mycothione and other disulfides and pyridine nucleotide analogues indicates a strict minimal disulfide substrate requirement for the glucosamine moiety of mycothione. The enzyme exhibits bi-bi ping-pong kinetics with both disulfide and quinone substrates. Transhydrogenase activity is observed using NADH and thio-NADP(+), confirming the kinetic mechanism. We suggest mycothione reductase as the newest member of the class I flavoprotein disulfide reductase family of oxidoreductases.
 ...
PMID:Expression, purification, and characterization of Mycobacterium tuberculosis mycothione reductase. 1051 39

The conserved residues of glutamyl tRNA reductase (GTR) from Hordeum vulgare (GTRhorvu) were found from an alignment/pile-up of 24 homologous sequences found using BLAST searches. A multiple alignment of sequences was used to obtain a prediction of the secondary structure of the GTR's. This secondary structure was submitted to the THREADER program to find possible homologous 3D structures. To help select the template for predicting the fold for GTRhorvu, we employed both molecular-biological and biochemical information about GTRhorvu. After fitting the secondary structure of GTRhorvu to the selected template, the MODELLER program was used to determine the fold for GTRhorvu. This model was built using the B subunit of succinyl CoA synthetase, 1scuB, as a template for the 3D structure of GTRhorvu. From the predicted structure, possible regions were identified for the binding of glutamyl-tRNA, NADPH and a heme inhibitor. The predicted structure was used to propose a detailed biochemical mechanism for the GTR, involving Mg catalyzed thioester formation and reduction by NADPH to glutamate-1-semialdehyde. Sites for these reactions are identified. The predicted structure has been deposited in the Brookhaven database as ID 1b61.
 ...
PMID:Predicted structure and fold recognition for the glutamyl tRNA reductase family of proteins. 1059 Nov 7

The metabolite 5-aminolevulinic acid (ALA) is an early committed intermediate in the biosynthetic pathway of heme and chlorophyll formation. In plants, 5-aminolevulinic acid is synthesized via a two-step pathway in which glutamyl-tRNA(Glu) is reduced by glutamyl-tRNA(Glu) reductase (GluTR) to glutamate 1-semialdehyde, followed by transformation to 5-aminolevulinic acid catalyzed by glutamate 1-semialdehyde aminotransferase. Using an Escherichia coli cell-based high-throughput assay to screen small molecule libraries, we identified several chemical classes that specifically inhibit heme/chlorophyll biosynthesis at this point by demonstrating that the observed cell growth inhibition is reversed by supplementing the medium with 5-aminolevulinic acid. These compounds were further tested in vitro for inhibition of the purified enzymes GluTR and glutamate 1-semialdehyde aminotransferase as confirmation of the specificity and site of action. Several promising compounds were identified from the high-throughput screen that inhibit GluTR with an I(0.5) of less than 10 microM. Our results demonstrate the efficacy of cell-based high-throughput screening for identifying inhibitors of 5-aminolevulinic acid biosynthesis, thus representing the first report of exogenous inhibitors of this enzyme.
 ...
PMID:Novel inhibitors of glutamyl-tRNA(Glu) reductase identified through cell-based screening of the heme/chlorophyll biosynthetic pathway. 1060 Jan 60

The oxidation of several metabolites in AS-30D tumor cells was determined. Glucose and glycogen consumption and lactic acid production showed high rates, indicating a high glycolytic activity. The utilization of ketone bodies, oxidation of endogenous glutamate, and oxidative phosphorylation were also very active: tumor cells showed a high respiration rate (100 ng atoms oxygen (min x 10(7) cells)(-1)), which was 90% oligomycin-sensitive. AS-30D tumor cells underwent significant intracellular volume changes, which preserved high concentrations of several metabolites. A high O(2) concentration, but a low glucose concentration were found in the cell-free ascites liquid. Glutamine was the oxidizable substrate found at the highest concentration in the ascites liquid. We estimated that cellular ATP was mainly provided by oxidative phosphorylation. These data indicated that AS-30D hepatoma cells had a predominantly oxidative and not a glycolytic type of metabolism. The NADH-ubiquinol oxido reductase and the enzyme block for ATP utilization were the sites that exerted most of the control of oxidative phosphorylation (flux control coefficient = 0.3-0.42).
 ...
PMID:Substrate oxidation and ATP supply in AS-30D hepatoma cells. 1068 45


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>