Abstract
Abstract An inducible oxidase from Arthrobacter oxydans that catalyzes the oxidation of 2,6-dihydroxypyridine was purified about 50-fold. Reduced pyridine nucleotide is required for oxidase activity; no requirement for ferrous, ferric, or other cation could be demonstrated. Artificial electron acceptors do not substitute for oxygen in the reaction. The oxidase catalyzes the anaerobic reduction of methylene blue by NADH. 2,6-Dihydroxypyridine increases the rate of the anaerobic reaction but is not altered during the reaction. The purified oxidase preparation has absorption maxima at 384 and 455 nm. The maxima disappear during the anaerobic reaction. These and other data suggest that the oxidase is a monooxygenase of molecular weight about 89,000 having a flavin prosthetic group. The only detectable product of the oxidase reaction is a blue pigment. Its formation is decreased or eliminated when oxidase is supplemented with a second enzyme fraction (cleavage enzyme). Blue pigment is not a substrate for the cleavage enzyme. It is proposed that the normal metabolic sequence is the oxidation of 2,6-dihydroxypyridine to a trihydroxypyridine, mediated by the oxidase, followed by pyridine ring cleavage in a second reaction. The over-all stoichiometry of the oxidase reaction, corrected for oxygen utilized in blue pigment formation, is 2,6-dihydroxypyridine:NADH:O2 = 1:1:1.
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