Reduced Nicotinamide Adenine Dinucleotide Oxidase Activity and H 2 O 2 Formation of Mycoplasma pneumoniae

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Abstract
Cell-free extracts of Mycoplasma pneumoniae showed two distinct reduced nicotinamide adenine dinucleotide (NADH 2 ) 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 NADH 2 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 NADH 2 oxidase activities of all fractions were relatively cyanide insensitive and were only minimally inhibited by flavoprotein and other respiratory chain inhibitors. H 2 O 2 formation was negligible unless FMN, but not flavine adenine dinucleotide (FAD), was added to the crude NADH 2 oxidase system; upon fractionation and electrophoresis, the H 2 O 2 formation was associated with the FMN-dependent, more rapidly moving NADH 2 oxidase band. This FMN-dependent NADH 2 oxidase-H 2 O 2 generating system may be a mechanism for the H 2 O 2 formation observed during glucose oxidation in the intact organism.

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