Nitrate reductase from Azotobacter chroococcum. Inactivation by oxidizing agents and reactivation with dithioerythritol

Treatment of a partially purified nitrate reductase preparation from the aerobic bacterium $\text{Azotobacter chroococcum}$ with a variety of oxidizing agents, such as glutathione, ferricyanide and illuminated flavins, results in inactivation of the enzyme. Independently of the mode of inactivation, incubation in the presence of dithioerythritol causes almost full recovery of nitrate reductase activity. Our data suggest that $\text{Azotobacter}$ nitrate reductase might be regulated through an interconversion process between an oxidized inactive form and a reduced active one.