A Nitrite Reductase from Achromobacter cycloclastes

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A nitrite reductase [EC 1. 7. 99. 3] was isolated from Achromobacter cycloclastes and characterized. The oxidized form of the enzyme had absorption maxima at 283, _??_400 (a shoulder), 464, 590 and 700mμ; the reduced form had no peak in the 400-800mμ region. The molecular weight was 69, 000. It had two copper atoms per molecule.
The enzyme catalyzed nitric oxide production from nitrite, whereby most part of the nitrite-nitrogen was converted to nitric oxide gas. Optimum pH of this reac-tion was 6.2. K_m for nitrite was estimated to be _??_5×10^-4M. This reaction was inhibited by KCN, diethyldithiocarbamate, p-chloromercuribenzoate and CO.
Nitrous oxide production from nitrite and hydroxylamine was also catalyzed by the enzyme.