Reduced Nicotinamide Adenine Dinucleotide Oxidase Activity and H2O2 Formation of Mycoplasma pneumoniae

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RESUMO

Cell-free extracts of Mycoplasma pneumoniae showed two distinct reduced nicotinamide adenine dinucleotide (NADH2) oxidase activities in the supernatant fraction. By ammonium sulfate fractionation and polyacrylamide gel electrophoresis, one activity not requiring flavine co-factors was precipitated by 50 to 70% ammonium sulfate concentration and identified with a slower-moving band on acrylamide gel electrophoresis; a second NADH2 oxidase activity was flavine mononucleotide (FMN) dependent and associated with a more rapidly moving band; it could only be partially precipitated by ammonium sulfate concentrations ranging from 50 to 100%. Studies with alternate electron acceptors indicated the presence of a menadione, a 2,6-dichlorophenol indophenol and a very weak ferricyanide oxido-reductase activity, but no cytochrome c oxido-reductase, in the cell-free preparations. The NADH2 oxidase activities of all fractions were relatively cyanide insensitive and were only minimally inhibited by flavoprotein and other respiratory chain inhibitors. H2O2 formation was negligible unless FMN, but not flavine adenine dinucleotide (FAD), was added to the crude NADH2 oxidase system; upon fractionation and electrophoresis, the H2O2 formation was associated with the FMN-dependent, more rapidly moving NADH2 oxidase band. This FMN-dependent NADH2 oxidase-H2O2 generating system may be a mechanism for the H2O2 formation observed during glucose oxidation in the intact organism.

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