PHOSPHORYLATION COUPLED TO NITRITE OXIDATION BY PARTICLES FROM THE CHEMOAUTOTROPH, NITROBACTER AGILIS

Abstract

A partially purified, particulate cytochrome-containing nitrite oxidase from Nitrobacter agilis is shown to exhibit phosphorylation coupled to the specific oxidation of nitrite. The presence of the oxidizable substrate nitrite and a phosphate acceptor such as ADP markedly enhances inorganic P32 phosphate incorporation into an organic P32 fraction. Add-ed magnesium ions also stimulate phosphorylation. ATP has been identified as the phosphorylation product when substrate quantities of ADP were used. When catalytic quantities of ADP are employed, virtually no organic P32 incorporation occurs unless a hexokinase "trapping system" is furnished in the reaction mixture. Other nucleotides such as IDP and GDP appear to serve as phosphate acceptors in place of ADP, whereas UDP and CDP are ineffective. Succinate and DPNH stimulate oxygen uptake at a rate which is 10 to 15% of that induced by nitrite, accompanied by a correspondingly small stimulation in organic P32 incorporation. Dinitrophenol, thyroxine, and dicumarol in concentrations as high as 5 x 10-5 M failed to uncouple the system. Higher concentrations of antimycin A and 2n-heptul-4-hydroxy-quinoline-N-oxide were also inhibitory.