ABSTRACT
The nature of air-inactivation of the formate dehydrogenase FdsDABG from Cupriavidus necator has been investigated. It is found that superoxide, generated in the reaction of reduced enzyme with oxygen, is responsible for the loss of activity and that superoxide dismutase protects the enzyme from air-inactivation. Inhibition appears to be due to the reaction of superoxide with the catalytically essential MoS group of the enzyme's molybdenum center in such a way that generates sulfite. SYNOPSIS: Superoxide generated in the reaction of reduced formate dehydrogenase FdsDABG from Cupriavidus necator with O2 is found to be responsible for the loss of activity. Catalytic amounts of superoxide dismutase are found to protect FdsDABG just as well as more generally used stabilizing inhibitors such as nitrate.