AUTOTROPHIC ENZYME SYSTEMS: I. ELECTRON TRANSPORT SYSTEMS CONCERNED WITH HYDROXYLAMINE OXIDATION IN NITROSOMONAS

Abstract

Intact cells or cell-free extracts of Nitrosomonas catalyze the rapid and stoichiometric conversion of nitrohydroxylamine to nitrite at rates comparable to the oxidation of ammonium ion or hydroxylamine to nitrite. Cell-free extracts possess a powerful hydroxylamine – cytochrome c reductase activating hydroxylamine to donate electrons to the cytochrome systems comprising b, c, and a type components. The partially purified enzyme complex is sensitive to low concentrations of cyanide and inhibitors of the flavoproteins. The possible mechanism of the formation and oxidation of the new intermediate "nitrohydroxylamine" in the reaction sequence is discussed.