Catalytic Mechanism of the Manganese Containing Superoxide Dismutase of Escherichia Coli Studied by Pulse Radiolysis Technique. Progress Report, 1September 1974--1July 1975.

摘要

The dismutation of O sub 2- ,catalyzed by E. coli Mn dismutase has been investigated. O sub 2-was generated in formate aqueous solutions by pulse radiolysis. When the initial concentration of O sub 2- , (O sub 2- ) sub 0is less than 10times the total concentration of the dismutase, (E) sub 0 , a reaction first order in both (O sub 2- ) and (E) sub 0is observed,the apparent reaction rate constant of which is (1.5 +- 0.15) x 10exp 9 M exp -1sec exp -1 . When (O sub 2- ) sub 0 /(E) sub 0greater than 15, a biphasic process is observed. Under these conditions only about 15 O sub 2-radical ions per each dismutase molecule react with a relatively fast rate. Excess O sub 2-is removed by a less efficient reaction,also first order in (E) sub 0and nearly first order in (O sub 2- ),which has an apparent rate constant (1.6 +- 0.25) x 10exp 8 M exp -8sec exp -1 . The results are interpreted in terms of four oxidation and reduction reactions.