Tetramethyl-p-phenylenediamine oxidase of Pseudomonas aeruginosa

An oxidase complex has been solubilized and partially purified from the membrane particle of Pseudomonas aeruginosa grown under limited oxygen condition. The oxidase consists of two major cytochrome components, cytochrome c554 and cytochrome o (b561), with a molar ratio of about 9:1 in terms of c-heme to protoheme content. Ninety percent of the cytochrome c+o complex, corresponding to all of the cytochrome c554, is reducible by reduced N,N,N',N'-tetramethyl-p-phenylenediamine. This partially purified oxidase exhibited a maximal specific activity about 5 mumol O2 uptake x min-1 x mg protein-1, with a Km (of reduced N,N,N',N'-tetramethyl-p-phenylenediamine) = 7.2 x 10(-4) M at 30 degrees C. The oxidase is sensitive to KCN, NaN3 and NaNO2. Oxidation-reduction potentiometric titration shows that cytochrome c554 has a midpoint potential of 289 mV and cytochrome o of + 25 mV at pH 7.2 in the partially purified oxidase preparation. The purity of the preparation has been estimated to be about 85--90% by gel electrophoresis.