Nitrite Reductase of Escherichia coli Specific for Reduced Nicotinamide Adenine Dinucleotide

Abstract

Kemp, John D. (University of California, Los Angeles), and Daniel E. Atkinson . Nitrite reductase of Escherichia coli specific for reduced nicotinamide adenine dinucleotide. J. Bacteriol. 92: 628–634. 1966.—A nitrite reductase specific for reduced nicotinamide adenine dinucleotide (NADH 2 ) appears to be responsible for in vivo nitrite reduction by Escherichia coli strain Bn. In extracts, the reduction product is ammonium, and the ratio of NADH 2 oxidized to nitrite reduced or to ammonium produced is 3. The Michaelis constant for nitrite is 10 μ m . The enzyme is induced by nitrite, and the ability of intact cells to reduce nitrite parallels the level of NADH 2 -specific nitrite reductase activity demonstrable in cell-free preparations. Crude extracts of strain Bn will also reduce hydroxylamine, but not nitrate or sulfite, at the expense of NADH 2 . Kinetic observations indicate that hydroxylamine and nitrite may both be reduced at the same active site. The high apparent Michaelis constant for hydroxylamine (1.5 m m ), however, seems to exclude hydroxylamine as an intermediate in nitrite reduction. In vitro activity is enhanced by preincubation with nitrite, and decreased by preincubation with NADH 2 .