A novel nonenzymatic pathway for the generation of nitric oxide by the reaction of hydrogen peroxide and D- or L-arginine.

Nitric oxide (NO) is a biologically active molecule known to be enzymatically synthesized from L-arginine in the presence of NO synthetase (NOS). In this study, we demonstrate a novel non-enzymatic pathway for NO synthesis involving hydrogen peroxide and D- or L-arginine. We employed two measures of NO generation. The first consists in the demonstration of the oxidative metabolites of NO (NO2 + NO3 = NOx) and the second is the confirmatory finding of chemiluminescence derived from NO. The results show that NOx increases in the incubation mixture containing hydrogen peroxide coupled with D-arginine, L-arginine, L-canavanine, and even the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). However, chemiluminescence was detected only from the reactions of hydrogen peroxide and D- or L-arginine and was diminished by the addition of carboxy-2-phenyl-4, 4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (PTIO), a specific scavenger of NO, confirming NO generation in the reaction.