Evidence for the Identity of the Nicotinamide Adenine Dinucleotide Phosphate-specific Sulfite and Nitrite Reductases of Escherichia Coli.

A reduced nicotinamide adenine dinucleotide phosphate (NADPH)-specific enzyme from Escherichiu wti, isolated as a nitrite reductase, catalyzed the reductions of both nitrite and hydroxylamine to ammonia, and the ratio of the two activities remained constant during partial purification (1). The demonstration in the same species of an NADPH-specific enzyme catalyzing the reductions of hydroxylamine and sulfite (2) led us to investigate the relation between the two preparations. This paper presents evidence suggesting that our nitrite reductase (1) and Mager’s sulfite reductase (2) are identical and that the physiological function of the enzyme is sulfite reduction.