A bacterial nitric oxide synthase from a Nocardia species.

Nitric oxide synthase (EC 1.14.23) was discovered in a Nocardia species. The bacterial nitric oxide synthase was purified as much as 380 fold by affinity chromatography over 2',5'-ADP-agarose. The partially purified enzyme required NADPH, O2, CA++, FAD, FMN, and tetrahydrobiopterin as cofactors in the conversion of L-arginine to L-citrulline and nitric oxide. The apparent Km for L-arginine was determined to be 8.2 microM, and the Vmax was 840 nmole NADPH consumed/min/mg protein. The enzyme was competetively inhibited by NG-nitro-arginine with an apparent Ki of 14.6 microM. The experimental evidence provides confirmation of the first microbial nitric oxide synthase in microorganisms.