Reduction of Ferric Iron Could Drive Hydrogen Tunneling in Lipoxygenase Catalysis: Implications for Enzymatic and Chemical Mechanisms

摘要

Recent kinetic measurements of the oxidation of linoleic acid by soybean lipoxygenase show that the thermal rate constants k_H=280 (+-12)s~-1 and k_D=5.0 (+-0.1)s~-1, are weakly temperature dependent within the temperature interval 30-50 deg C. The primary kinetic k_H/k_D isotope effect is almost temperature independent, and is one order of magnitude larger than expected for a single rate determining isotopically sensitive step.