Oxygen activation in neuronal NO synthase: resolving the consecutive mono-oxygenation steps.

摘要: The vital signalling molecule NO is produced by mammalian NOS (nitric oxide synthase) enzymes in two steps. L-arginine converted into NOHA (Nω-hydroxy-L-arginine), which and citrulline. Both steps are thought to proceed via similar mechanisms the cofactor BH4 (tetrahydrobiopterin) activates dioxygen at haem site electron transfer. subsequent events poorly understood due lack of stable intermediates. By analogy with cytochrome P450, a haem-iron oxo species may be formed, or direct reaction between haem-peroxy intermediate substrate occur. also occur different mechanisms. In present paper we analyse using G586S mutant nNOS (neuronal NOS), introduces an additional hydrogen bond active provides proton source. enzyme, as wild-type but interesting then observed. This stabilized form oxygenating species. able perform step 2 (reaction NOHA), not 1 (with L-arginine) indicating that extra enables it discriminate mono-oxygenation implies follow chemical