Assay and characterization of the NO dioxygenase activity of flavohemoglobins

A variety of hemoglobins, including several microbial flavohemoglobins, enzymatically dioxygenate the free radical nitric oxide (*NO) to form nitrate. Many of these *NO dioxygenases have been shown to control *NO toxicity and signaling. Furthermore, *NO dioxygenation appears to be an ancient and intrinsic function for members of the hemoglobin superfamily found in Archaea, eukaryotes, and bacteria. Yet for many hemoglobins, a function remains to be elucidated. Methods for the assay and characterization of the *NO dioxygenase (EC 1.14.12.17) activity and function of flavohemoglobins are described. The methods may also be applied to the discovery and design of inhibitors for use as antibiotics or as modulators of *NO signaling.