PERACID OXIDATION OF AN N-HYDROXYGUANIDINE COMPOUND - A CHEMICAL-MODEL FOR THE OXIDATION OF N-OMEGA-HYDROXY-L-ARGININE BY NITRIC-OXIDE SYNTHASE

Arginine is oxidized by a class of enzymes called the nitric oxide syn thases (NOS) to generate citrulline and, presumably, nitric oxide (.NO ). N-Hydroxylation of a guanidinium nitrogen of arginine to generate N -hydroxyarginine (NOHA) has been shown to be a step in the biosynthesi s of .NO. In an effort to elucidate the mechanism by which further oxi dation of NOHA occurs, the oxidation of a model N-hydroxyguanidine com pound by several peracids was studied in depth. This oxidative chemist ry is a possible model for the enzymatic process since the correspondi ng urea (or citrulline equivalent product) is obtained along with an o xidized nitrogen species. The oxidized nitrogen product was, however, not .NO but rather HNO. .NO generation in this chemical system and in the enzymatic process would require another one-electron oxidation. Th e mechanistic details of this are further discussed.