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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined the unitrophic metabolism of acetate and methanol individually and the mixotrophic utilization of these compounds by using detailed (14)C-labeled tracer studies in a strain of Methanosarcina barkeri adapted to grow on acetate as the sole carbon and energy source. The substrate consumption rate and methane production rate were significantly lower on acetate alone than during the unitrophic or mixotrophic metabolism of methanol. Cell yields (in grams per mole of substrate) were identical during exponential growth on acetate and exponential growth on methanol. During unitrophic metabolism of acetate, the methyl moiety accounted for the majority of the CH(4) produced, but 14% of the CO(2) generated originated from the methyl moiety. This correlated with the concurrent reduction of equivalent amounts of the C-1 of acetate to CH(4). (14)CH(4) was also produced from added (14)CO(2), although to a lesser extent than from reduction of the C-1 of acetate. During mixotrophic metabolism, methanol and acetate were catabolized simultaneously. The rates of (14)CH(4) and (14)CO(2) generation from [2-(14)C]acetate were logarithmic and higher in mixotrophic than in unitrophic cultures at substrate concentrations of 50 mM. A comparison of the oxidoreductase activities in cell extracts of the acetate-adapted strain grown on acetate and of strain MS grown on methanol or on H(2) plus CO(2) indicated that the pyruvate, alpha-ketoglutarate, and isocitrate dehydrogenase activities remained constant, whereas the CO dehydrogenase activity was significantly higher (5,000 nmol/min per mg of protein) in the acetate-adapted strain. These results suggested that a significant intramolecular redox pathway is possible for the generation of CH(4) from acetate, that energy metabolism from acetate by M. barkeri is not catabolite repressed by methanol, and that the acetate-adapted strain is a metabolic mutant with derepressed CO dehydrogenase activity.
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PMID:Comparison of unitrophic and mixotrophic substrate metabolism by acetate-adapted strain of Methanosarcina barkeri. 679 21

A soluble yellow CO dehydrogenase from CO-autotrophically grown cells of Pseudomonas carboxydohydrogena was purified 35-fold in seven steps to better than 95% homogeneity with a yield of 30%. The final specific activity was 180 mumol of acceptor reduced per min per mg of protein as determined by an assay based on the CO-dependent reduction of thionin. Methyl viologen, nicotinamide adenine dinucleotide (phosphate), flavin mononucleotide, and flavin adenine dinucleotide were not reduced by the enzyme, but methylene blue, thionin, and toluylene blue were reduced. The molecular weight of native enzyme was determined to be 4 x 10(5). Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate revealed at least three nonidentical subunits of molecular weights 14,000 (alpha), 28,000 (beta), and 85,000 (gamma). The ratio of densities of each subunit after electrophoresis was about 1:2:6 (alpha/beta/gamma), suggesting an alpha(3)beta(3)gamma(3) structure for the enzyme. The purified enzyme was free of formate dehydrogenase and nicotinamide adenine dinucleotide-specific hydrogenase activities, but contained particulate hydrogenase-like activity with thionin as electron acceptor. Known metalchelating agents tested had no effect on CO dehydrogenase activity. No divalent cations tested stimulated enzyme activity. The native enzyme does not contain Ni since cells assimilated little (63)Ni during growth, and the specific (63)Ni content of the enzyme declined during purification. The isoelectric point of the native enzyme was found to be 4.5 to 4.7. The K(m) for CO was found to be 63 muM. The spectrum of the enzyme and its protein-free extract revealed that it contains bound flavin. The cofactor was flavin adenine dinucleotide based on enzyme digestion and thin-layer chromatography. One mole of native enzyme contains at least 3 mol of noncovalently bound flavin adenine dinucleotide.
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PMID:Purification and some properties of carbon monoxide dehydrogenase from Pseudomonas carboxydohydrogena. 689 15

In cell suspension of Desulfovibrio desulfuricans B-1388, oxidation of CO as the only energy source is associated with reduction of SO42-. After a 2-h incubation of cells in 8% CO, 81% of the gas is converted. Oxidation of 1 mole CO results in formation of 0.23 mole H2S. Intracellular ATP content increases from 2.5 (control) to 8.3 nmoles/mg (during CO conversion). Dinitrophenol inhibits sulfate reduction and CO oxidation. CO dehydrogenase was detected in cytoplasmic and membrane cell fractions (59 and 34%, respectively).
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PMID:Energetic aspects of CO oxidation in desulfovibrio desulfuricans 986 47