THE OXIDATION OF l-MALATE BY PSEUDOMONAS SP.

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Abstract
Although the tricarboxylic -acid cycle and (on appropriate substrates) the glyoxylate cycle function in Pseudomonas ovalis Chester, cell-free extracts of this organism did not catalyze the reduction of either reduced nicotinamide-adenine dinucleotide (NADH2) or reduced nicotinamide-adenine-dinucleotide phosphate (NADPH2) by oxaloacetate. They are free of L-malate dehydrogenases that are dependent on exogenous nicotinamide nucleotides for activity. Cell-free extracts of P. ovalis Chester contain an L-malate-oxidase system that can oxidize L-malate to oxaloacetate, with O2, phenazine[long dash]metho-sulfate, 2,6-dichlorophenolindophenol, ferricyanide or cytochrome-c as electron acceptor. In no case was the activity influenced by added nicotinamide nucleotides. The L-malate-oxidase system was bound to the cell-wall membrane. The aerobic oxidation of L-malate by this system involves flavoprotein and cytochromes. The oxidation of L-malate in the presence of O2, phenazine-methosulfate or 2,6-dichloro-phenol-indophenol was markedly inhibited by 2 mM-sodium Amytal. The inhibition decreased as the substrate concentration was lowered.