EC Explorer

1.14.13.250

nitrosourea synthase

N^ω-methyl-L-arginine + 2 NADH + 2 H⁺ + 3 O₂ = N^δ-hydroxy-N^ω-methyl-N^ω-nitroso-L-citrulline + 2 NAD⁺ + 3 H₂O (overall reaction);;(1a) N^ω-methyl-L-arginine + NADH + H⁺ + O₂ = N^δ-hydroxy-N^ω-methyl-L-arginine + NAD⁺ + H₂O;;(1b) N^δ-hydroxy-N^ω-methyl-L-arginine + NADH + H⁺ + O₂ = N^δ,N^ω;-dihydroxy-N^ω-methyl-L-arginine + NAD⁺ + H₂O;;(1c) N^δ,N^ω;-dihydroxy-N^ω-methyl-L-arginine + O₂ = N^δ-hydroxy-N^ω-methyl-N^ω-nitroso-L-citrulline + H₂O

sznF (gene name), StzF

N^ω-methyl-L-arginine,NADH:oxygen oxidoreductase (N^δ-hydroxy-N^ω-methyl-N^ω-nitroso-L-citrulline-forming)

The enzyme, characterized from the bacterium Streptomyces achromogenes subsp. streptozoticus, catalyses a complex multi-step reaction during the biosynthesis of the glucosamine-nitrosourea antibiotic streptozotocin. The overall reaction is an oxidative rearrangement of the guanidine group of N^ω-methyl-L-arginine, generating an N-nitrosourea product. The enzyme hydroxylates its substrate at the N^δ position, followed by a second hydroxylation at the N^ω′ position. It then catalyses an oxidative rearrangement to form N^δ-hydroxy-N^ω-methyl-N^ω-nitroso-L-citrulline. This product is unstable, and degrades non-enzymically into nitric oxide and the denitrosated product N^δ-hydroxy-N^ω-methyl-L-citrulline. The enzyme contains two active sites, each of which utilizes a different iron-containing cofactor.

created 2021