The kinetics of methyl viologen oxidation and reduction by the hydrogenase from Clostridium pasteurianum.
A mechanism for the reduction and oxidation of methyl viologen by Clostridium pasteurianum hydrogenase (hydrogen:ferredoxin oxidoreductase, EC 1.12.7.1) is proposed. Double reciprocal plots for methyl viologen reduction and oxidation at pH values 7.0-9.85 are linear, and the plots for reduction and oxidation are intersecting. Such data are consistent with a mechanism in which the H2 and one methyl viologen bind (either in order or randomly) with subsequent reduction and release of the methyl viologen. A second methyl viologen then is bound, reduced and released. Comparison of the calculated Keq' with the Haldane expression in which both methyl viologens react at the same rate show a large difference. This difference indicates that the two methyl viologens react at different rates. Addition of oxidized electron carriers inhibits the hydrogen-deuterium exchange reaction (i.e., the exchange of protons between H2 and 2H2O). CO reversibly inhibits methyl viologen reduction and is competitive vs. H2. O2 acts as an irreversible inhibitor.
D002248:Carbon Monoxide / Q000494:pharmacology; D003013:Clostridium / Q000201:enzymology*; D003903:Deuterium; D005288:Ferredoxins; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008751:Methylene Blue / Q000494:pharmacology; D008956:Models, Chemical; D010088:Oxidoreductases / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology; D010269:Paraquat / Q000378:metabolism*; D013379:Substrate Specificity
D005288:Ferredoxins; D002248:Carbon Monoxide; D006859:Hydrogen; D003903:Deuterium; D010088:Oxidoreductases; D010269:Paraquat; D010100:Oxygen; D008751:Methylene Blue