Mechanisms of Electron Transfer in Catalysis by Copper Zinc Superoxide Dismutase

摘要

Understanding the origins of oxidation-reduction catalysis by metalloenzymes requires detailed information concerning the mechanisms of electron transfer (ET).Copper zinc superoxide dismutase (SOD) is perhaps the most thoroughly studied member of a family of exceptionally well-tuned catalysts for the dismutation of superoxide: 2O_2~(centre dot-) + 2H~+ -> O_2 + H_2O_2.Under physiological conditions,the rate of the enzymatic reaction is approx 10~4 times faster than that of the spontaneous disproportionation of O_2~(centre dot-) in solution.The origin of enzyme catalysis with respect to the near barrierless nature of ET has not been understood,yet this enhanced reactivity is the basis of SOD's protective function against physiological oxidative damage.