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

Isolated perfused rat lungs were used to investigate effects of paraquat on lung glucose metabolism. Lungs were ventilated with 5% CO2 in air and perfused with Krebs-Ringer bicarbonate buffer, pH 7.4, containing albumin and 5.5 mM radiolabeled D-glucose. Control lung glucose utilization, estimated from rate of 3H2O production from [5-3H]glucose, was 44 mumol/h-g dry wt. Pentose cycle activity, based on 14CO2 specific yields at the end of perfusions with [1-14C]- and [6-14C]glucose, was 14% of glucose utilization. During perfusion with 1.5 mM paraquat, glucose utilization increased 28%, 14CO2 production via the pentose cycle increased 182% (P less than 0.005), CO2 production via mitochondrial metabolism increased 39% (P less than 0.02), and the rate of lactate production increased 28% (P less than 0.05). Pyruvate production and the lactate-to-pyruvate ratio were not significantly altered. The data indicate that interaction of paraquat with the lung results in increased turnover of cytoplasmic NADPH and increased mitochondrial metabolism, but no significant change in cytoplasmic redox state. The findings are compatible with intracellular enzymatic reduction of paraquat by an NADPH-requiring reductase.
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PMID:Alterations of glucose metabolism during perfusion of rat lung with paraquat. 2 1

Reduced ferredoxin:CO2 oxidoreductase (CO2 reductase) from Clostridium pasteurianum catalyzes the reduction of 'CO2' to formate with reduced ferredoxin, an isotopic exchange between 'CO2' and formate in the absence of ferredoxin, and the oxidation of formate to 'CO2' with oxidized ferredoxin. The active species of 'CO2', i.e. CO2 or HCO3 (H2CO3), utilized by the enzyme was determined. The method employed for the species identification was that of Copper et al. (1968). Both 'CO2' reduction to formate and the exchange reaction were studied. Data were obtained which are compatible with those expected if CO2 is the active species. The V and the dissociation constant Ks of the enzyme - CO2 complex in dependence of pH were determined from initial velocity studies of the exchange reaction. V was found to be only slightly affected by pH between 5.5 and 7.5. Ks was markedly dependent on pH; the constant increased with decreasing pH from 0.2 mM at pH 7.5 to 3 mM at pH 5.5.
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PMID:The active species of 'CO2' utilized by reduced ferredoxin:CO2 oxidoreductase from Clostridium pasteurianum. 24 Jun 89

Reduced ferredoxin: CO2 oxidoreductase (CO2-reductase) from Clostridium pasteurianum catalyzes the reduction of CO2 to formate at the expense of reduced ferredoxin, an isotopic exchange between CO2 and formate in the absence of ferredoxin, and the oxidation of formate to CO2 with oxidized ferredoxin. The three activities were found to be equally affected by monovalent anions known to be ligands to transition metals: The enzyme was reversibly inhibited by azide (Ki = 0.004mM), cyanate (Ki = 0.3 mM), thiocyanate (Ki = 1mM), nitrite (Ki = 0.4mM), nitrate (Ki = 6mM), chlorate (Ki = 3mM), fluoride (Ki = 5mM), and by chloride, bromide, iodide (Ki greater than 5mM). There was no observable effect of pH on the inhibition constants. The enzyme was not inhibited by carbon monoxide. The enzyme was irreversibly inactivated by low concentrations (10muM) of cyanide. The rate of inactivation increased with increasing pH with an inflection point near pH 9.5. Reduced ferredoxin and formate rather than oxidized ferredoxin or CO2 protected the enzyme from inactivation by cyanide. The enzyme was protected by azide and cyanate from inactivation. In the presence of high concentrations of the monovalent anions the rate of inactivation by heat (55 degrees C), by molecular oxygen, and by cyanide was decreased by a factor of more than 100. Half maximal protection was observed at the Ki concentrations of the two reversible inhibitors. The data are interpreted to indicate that a transition metal of weak "a class" character and a disulfide are catalytically significant groups of CO2-reductase from C. pasteurianum.
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PMID:Reduced ferredoxin: CO2 oxidoreductase from Clostridium pasteurianum. Effect of ligands to transition metals on the activity and the stability of the enzyme. 24 89

The effects of a wide variety of oxygenated sterols upon sterol biosynthesis and hydroxymethylglutaryl-CoA reductase (mevalonate: NADP+ oxidoreductase (CoA-acylating), EC 1.1.1.34) activity in a wild-type clone and in a 25-hydroxycholesterol-resistant clone of Chinese hamster lung (Dede) cells are described. Derivatives of cholesterol which were oxygenated in the 6, 7 or 15 positions of the sterol nucleus or in the 20, 22, 24 or 25 positions of the sterol side chain were shown to be potent inhibitors of sterol synthesis and reductase activity in the wild-type cells but none of these substitutions had any effect on the 25-hydroxycholesterol-resistant A2 clone. A 32-hydroxylated derivative of lanosterol also suppressed sterol synthesis and reductase activity in wild-type cells but had no significant effect upon the A2 line. It was also appraent that a complete sterol side chain was necessary for inhibitory activity. Studies of a wide range of inhibitory sterols indicated that there was a close correlation between their effects upon sterol synthesis and reductase activity and that their inhibitory action was specific for sterol biosynthesis since little effect was observed upon fatty acid or CO2 synthesis. Previous studies had shown that the uptake of 25-hydroxycholesterol by the resistant A2 line was unimpaired and the present results indicate that metabolism of this oxygenated sterol is also unaltered. These results, in conjunction with previous studies, suggest that the resistant A2 line is defective in feedback regulation of cholesterol synthesis and that all of the oxygenated sterols tested suppress the biosynthetic pathway through at least one common step.
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PMID:Effects of various oxygenated sterols on cellular sterol biosynthesis in Chinese hamster lung cells resistant to 25-hydroxycholesterol. 50 85

Mutants of Escherichia coli K12 strain WGAS-GF+/LF+ were selected for their inability to use fumarate as terminal electron acceptor for supporting growth on glycerol or lactate in an atmosphere of H2 plus 5% CO2. Eighty-three mutants were grouped into seven different categories according to their ability to grow on different media and their ability to produce gas during glucose fermentation. Enzymological and genetic studies indicated that the major class (type I), representing nearly 70% of the isolates, lacked fumarate reductase and corresponded to the frdA mutants studied previously (Spencer & Guest, 1973, 1974). Members of a second class (type II) were phenotypically similar to men mutants, blocked in menaquinone biosynthesis. They differed from menA mutants in having lesions in the 44 to 51 min region of the chromosome rather than at 87 min. It was concluded that fumarate reductase and menaquinone are essential for anaerobic growth when fumarate serves as electron acceptor but not when nitrate performs this function. Fumarate reductase and menaquinone are also essential for H2-dependent growth on fumarate. Type III mutants, originally frdB, were designated fnr because they were defective in fumarate and nitrate reduction and impaired in their ability to produce gas. The fnr gene was located at 28-5 min by its cotransducibility with pyrF (5-7 to 9-2%) and trpA (2-7 to 5-7%) and the gene order fnr-qmeA-pyrF-trpA was established. It was not possible to assign specific metabolic lesions to the fnr mutants nor to the remaining classes, which all exhibited pleiotropic phenotypes. Nevertheless, the results demonstrate that functional or organizational relationships exist between the fumarate reductase system, nitrate reduction and hydrogen production.
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PMID:Mutants of Escherichia coli K12 unable to use fumarate as an anaerobic electron acceptor. 79 7

A ferredoxin containing only one [Fe4S4] cluster was purified from Clostridium thermoaceticum. It has a molecular weight of about 7,300, a partial specific volume of 0.67, and an isoelectric point of 3.25. Its absorption spectrum has two maxima at 390 nm (epsilon = 16.8 X 10(3)M-1cm-1) and at 280 nm (epsilon = 24.2 X 10(3)M-1cm-1). The absorption at 390 nm is almost half that of other clostridial ferredoxins, which have two [Fe4S4] clusters, and is similar to other ferredoxins with only one [Fe4S4] cluster. The ferredoxin had high thermal stability and retained over 50% of its activity after treatment at 80 degrees C. It functions in the transfer of electrons from pyruvate to nicotinamide adenine dinucleotide phosphate (NADP), which indicates the presence of pyruvate:ferredoxin oxidoreductase and reduced ferredoxin-NADP reductase in C, thermoaceticum. NADPH is used in the synthesis of acetate from CO2 in this organism.
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PMID:A four-iron, four-sulfide ferredoxin with high thermostability from Clostridium thermoaceticum. 86 52

The pyruvate dehydrogenase complex from Axotobacter vinelandii was isolated in a five-step procedure. The minimum molecular weight of the pure complex is 600,000, as based on an FAD content of 1.6 nmol-mg protein-1. The molecular weight is 1.0-1.2 X 10(6), indicating 1 mole of lipoamide dehydrogenase dimer per complex molecule. Sodium dodecylsulphate gel electrophoretical patterns show that apart from pyruvate dehydrogenase (Mr89,000) and lipoamide dehydrogenase (Mrmonomer 56,000) two active transacetylase isoenzymes are present with molecular weight on the gel 82,000 and 59,000 but probably actually lower. The pure complex has a specific activity of the pyruvate-NAD+ reductase (overall) reaction of 10 units-mg protein-1 at 25 degrees C. The partial reactions have the following specific activities in units-mg protein-1 at 25 degrees C under standard conditions: pyruvate-K3Fe(CN)6 reductase 0.14, transacetylase 3.6 and lipoamide dehydrogenase 2.9. The properties of this complex are compared with those from other sources. NADPH reduced the FAD of lipoamide dehydrogenase as well in the complex as in the free form. NADP+ cannot be used as electron acceptor. Under aerobic conditios pyruvate oxidase reaction, dependent on Mg2+ and thiamine pyrophosphate, converts pyruvate into CO2 and acetate; V is 0.2 mumol 02-min-1-mg-1, Km(pyruvate)0.3 mM. The kinetics of this reaction shows a linear 1/velocity-1/[pyruvate] plot. K3Fe(CN)6 competes with the oxidase reaction. The oxidase activity is stimulated by AMP and sulphate and is inhibited by acetyl-CoA. The partially purified enzyme contains considerable phosphotransacetylase activity. The pure complex does not contain this activity. The physiological significance of this activity is discussed.
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PMID:The pyruvate-dehydrogenase complex from Azotobacter vinelandii. 120 21

Dihydrouracil dehydrogenase (NADP+) (EC 1.3.1.2) was partially purified from the cytosol fraction of rat liver and fractionated by disc gel electrophoresis. A major and minor band were visualized by staining for enzyme activity. The substrate specificity of these bands was investigated. It was found that both bands were two to three times more active with dihydrothymine as substrate than with dihydrouracil in the presence of NADP+ and the optimum pH of 7.4. Mitochondrial fractions containing most of the NADH-dependent uracil reductase of rat liver cells were fractionated by centrifugation in sucrose density gradients. Two procedures involving linear or discontinuous gradients were used. By both, good separation of NADH- and NADPH- dependent reductases was achieved. Marker enzyme studies supported the view that the NADH-dependent enzyme is located principally in mitochondria whereas the NADPH-dependent enzyme is mainly in plasma and endoplasmic reticulum membranes. For the NADH-dependent reductase the apparent Km for thymine at pH 7.4 was 1.39 times that found for uracil whereas for the NADPH-dependent enzyme the apparent Km values were similar for the two substrates at this pH. Dihydrouracil was the principal product isolated by paper chromatography from the reaction mixture containing a partially purified fraction of mitochondria, uracil and NADH at pH 7.4. This fraction also catalyzed the formation of radioactive carbon dioxide from [2-14C]uracil. The proportion of CO2 formed by the mitochondria was about 10% of that formed by the original homogenate.
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PMID:Pyrimidine reducing enzymes of rat liver. 126 May

Topical lovastatin stimulates epidermal fatty acid synthesis in vivo; therefore, studies were undertaken to examine the effects of HMG-CoA reductase inhibitors on fatty acid metabolism in cultured keratinocytes. When exposed to fluindostatin or lovastatin for greater than or equal to 24 h, keratinocytes in serum-free media accumulated nile red-fluorescent lipid droplets. By 72 h, the triacylglycerol and phospholipid content were increased 2.5- and 1.3-fold, respectively. Reductase inhibitors (1-10 microM) increased fatty acid synthesis approximately 1.5-fold; increased synthesis was noted only after greater than 15 h exposure and was distributed among phospholipids and triacylglycerols. Oxidation of [14C]palmitate to CO2 was decreased greater than 50% in inhibitor-treated cultures, and label accumulated in triacylglycerols. Inhibitor-treated keratinocytes exhibited increased numbers of peroxisomes, using diaminobenzidene ultracytochemistry. Peroxisomal hyperplasia was also demonstrated by increased catalase activity (1.5- to 2.5-fold), increased dihydroxyacetone phosphate acyltransferase activity (1.4-fold) and increased peroxisomal (KCN-insensitive) fatty acid oxidation (1.4-fold) in inhibitor-treated cultures. Thus HMG-CoA reductase inhibitors increase fatty acid synthesis, induce triacylglycol and phospholipid accumulation, and induce peroxisomes in cultured keratinocytes. Coincubations with either low density lipoproteins or 25-hydroxycholesterol prevented both the peroxisomal hyperplasia and increased fatty acid synthesis, suggesting that these effects of reductase inhibitors may be linked to their effects on the cholesterol biosynthetic pathway.
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PMID:HMG-CoA reductase inhibitors perturb fatty acid metabolism and induce peroxisomes in keratinocytes. 156 72

Methylenetetrahydromethanopterin reductase from metanogenic archaebacteria catalyzes the reversible reduction of N5,N10-methylenetetrahydromethanopterin to N5-methyltetrahydromethanopterin with reduced coenzyme F420 as electron donor. The enzyme is involved in methane formation from CO2 and in methanol disproportionation to CO2 and CH4. We report here that the reductase from Methanobacterium thermoautotrophicum specifically binds to Blue Sepharose CL-6B. Binding was competitive with coenzyme F420 rather than with NAD, NADP, FAD, FMN, AMP, ADP and ATP. The reductase could also be desorbed with salt. Based on this property an affinity chromatographic procedure for the purification of the enzyme was developed.
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PMID:Single step purification of methylenetetrahydromethanopterin reductase from Methanobacterium thermoautotrophicum by specific binding to blue sepharose CL-6B. 169 53


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