Title: Changing SOX in a Flash: Chemistry of a Vital Molybdenum Enzyme

Abstract: Sulfite oxidase (SO) catalyzes the final step in the degradation of sulfur-containing amino acids and is critical in detoxifying excess sulfite. Human SO deficiency is a fatal genetic disorder that leads to early death, and impaired SO activity is implicated in sulfite neurotoxicity. Intraprotein electron transfer (IET) between the Mo and Fe centers in SO can be studied by laser flash photolysis in the presence of deazariboflavin. Conformational change is involved in the IET of SO, and electrostatic interactions may play a major role in guiding the docking of the heme domain to the Mo domain prior to electron transfer. Point mutations in human SO can result in significantly impaired IET or no IET, thus rationalizing their fatal effects.