Perferryl complex of nitric oxide synthase: role in secondary free radical formation.

Neuronal nitric oxide synthase (NOS I) has been shown to generate nitric oxide (NO*) and superoxide (O(2)*-)during enzymatic cycling, the ratio of each free radical is dependent upon the concentration of L-arginine. Using spin trapping and electron paramagnetic resonance (EPR) spectroscopy, we recently reported that NOS I can oxidize ethanol (EtOH) to alpha-hydroxyethyl radical (CH(3)*CHOH). We speculated that the perferryl complex of NOS, (NOS-Fe(5+)[double bond]O) was responsible for the generation of CH(3)CHOH. Using potassium monopersulfate (KHSO(5)) to oxidize the heme of NOS I to NOS-Fe(5+)[double bond]O, we were able to demonstrate that this perferryl complex can oxidize L-arginine to L-citrulline and NO. Even in the absence of L-arginine, EtOH was oxidized to CH(3)*CHOH by NOS-Fe(5+)[double bond]O. Sodium cyanide (NaCN), a heme blocker, inhibited the formation of CH(3)*CHOH by NOS.