AMMONIUM OXIDATION BY CELL-FREE EXTRACTS OF ASPERGILLUS WENTII

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Abstract
Cell-free extracts of Aspergillus wentii were found to catalyze the oxidation of ammonium to nitrate; small quantities of hydroxylamine and nitrite accumulated during the oxidation. The oxidations of hydroxylamine to nitrite and of nitrite to nitrate apparently took place through the respective cytochrome c reductases. Added nicotinamide adenine dinucleotide phosphate and mammalian cytochrome c stimulated the oxidations of ammonium, hydroxylamine, and nitrite. Added iron increased the rate of nitrate formation from ammonium. Allylthiourea did not inhibit ammonium oxidation. The similarities and differences between autotrophic and heterotrophic nitrification are discussed.