Mechanistic studies of nitrite reactions with metalloproteins and models relevant to mammalian physiology

This review provides a summary of reaction mechanisms involving the interactions of nitrite ion with metal centers relevant to physiology. The majority of the systems that have been investigated are heme proteins and models, where nitrite reacts with the central metal ions to generate important iron-NOx intermediates and subsequent NOx products. We also discuss reactions with other potentially relevant systems. Nitrite is formed as a product of NO autoxidation in aqueous media and can be formed by the bacterial reduction of ingested nitrate as well. It is now generally accepted that under certain conditions nitrite, which is present in mammalian fluids and tissue at micromolar concentrations, can serve as a biological reserve of the bioregulatory agent nitric oxide. However, it is possible that nitrite serves other functions as well. The goal of this review is to evaluate the present state of understanding regarding these pathways and the delicate interplay between nitrite and the various NOx species of biological relevance.