Abstract
Methyl viologen-linked nitrite reductase (EC 1.7.7. 1), an enzyme which catalyzes the 6-electron reduction of nitrite to ammonia, was isolated from bean roots. The isolated enzyme was homogeneous by disc electrophoresis with polyacrylamide gel. The molecular weight of the enzyme was estimated to be 62, 000 by SDS-polyacrylamide gel electrophoresis. In the oxidized form, the enzyme had absorption maxima at 280, 397 (Soret band), 535, and 573 nm (α band), indicating that siroheme is directly involved in the catalysis of nitrite reduction. The absorbance ratios, A391 : A280 and A573 : A397, were 0.3 and 0.39, respectively. Antiserum to spinach leafnitrite reductase failed to give a positive Ouchterlony result with bean root nitrite reductase, but this antiserum did inhibit the activity of the latter enzyme.
