Nitrite-dependent nitric oxide synthesis by molybdenum enzymes

Nitric oxide (NO) is an important gasotransmitter involved in numerous intra- and intercellular signaling events. In addition to the oxidative pathway of NO generation, which includes three NO synthase (NOS) isoforms in mammals, a reductive pathway contributes to NO generation. In this pathway, nitrite is reduced to NO by various metal-containing proteins. Among these, all members of the eukaryotic molybdenum (Mo)-dependent enzyme family were found to be able to reduce nitrite to NO. This Review focuses on the current state of research in the field of Mo-dependent nitrite reduction in eukaryotes. An overview on the five eukaryotic Mo-enzymes is given, and similarities as well as differences in their nitrite reduction mechanisms are presented and discussed in the context of physiological relevance.