Mechanism of the inhibition of catalase by ascorbate. Roles of active oxygen species, copper and semidehydroascorbate.

摘要: Ascorbate reversibly inhibits catalase, and this inhibition is enhanced rendered irreversible by the prior addition of copper(II)-bishistidine. In absence copper, was prevented reversed ethanol, but not superoxide dismutase, benzoate, mannitol, thiourea, desferrioxamine, or DETAPAC. presence copper complex dismutase still had no effect, DETAPAC, additional histidine decreased extent inactivation to that seen in copper. ethanol protected at [ascorbate] less than 1 mM, ineffective greater 2 even oxygen. Although complete removal oxygen provided full protection against ascorbate, if catalase briefly preincubated with H2O2 flushing nitrogen, present. fact, present, Increasing concentration from ambient 100% slowed inactivation, whether It concluded initial reversible involves reaction form compound I, followed one electron reduction I II. added (reversible) allows accumulate sufficiently permit inactivation. Since required, neither nor conventional scavengers active forms oxygen, likely mediated semidehydroascorbate, and/or it may involve site-specific generation damaging intermediates.