Structure, reactivity and function of bacterial nitric oxide synthases

Abstract

Nitric oxide synthases (NOSs) from higher organisms are heme‐based mono‐oxygenases that catalyze the conversion of L‐arginine (L‐arg) to nitric oxide (NO), a potent signaling molecule and cytotoxic agent. Bacterial homologs of mammalian NOSs (mNOSs) have recently been characterized in a subset of mostly gram‐positive bacteria. Crystallographic and spectroscopic analyses of bacterial NOSs bound to substrates, intermediates and inhibitors provide insights into structural and chemical properties important for this enzyme family to produce NO. In particular, NOSs isolated from thermophilic bacteria have slower reaction profiles than their mesophilic counterparts. This property has proved useful for the characterization of oxy‐heme species. The biological roles of bacterial NOS appear to differ from those of mNOS, but overall, they are not well understood. Nevertheless, studies of bacterial NOSs show great promise for unraveling new functions for NO in prokaryotes.