Reactions of Cytochrome b1 and Nitrate Reductase in a Preparation Solubilized from Escherichia coli*

Abstract
The solubilized nitrate reductase system from E. coli possessed enzyme system(s), by which formate- or vitamin K3-reduced cytochrome b1 was reoxidized by 02, nitrate or chlorate. Reoxidation by O2 was not inhibited by cyanide or azide, but by nitrate or chlorate; it was sensitive to cyanide-and azide-inhibition. Participation of the flavin derivative was proved. Oxidation of cytochrome b1 by nitrate was strongly inhibited by 2-heptyl-4-hydroxyquinoline-N-oxide.