Characterization of a transient covalent adduct formed during dimethylarginine dimethylaminohydrolase catalysis

A study is carried out on the dimethylarginine dimethylaminohydrolase (DDAH) that regulates the concentrations of human endogenous inhibitors of nitric oxide synthase, N(sub omega)-methyl-L-arginine (NMMA), and asymmetric N(sub omega), N(sub omega)-dimethyl-L-arginine (ADMA). The studies demonstrate that covalent adduct was attached to an active site residue and implicates Cys249 as the catalytic nucleophile required for intermediate formation.