KINETICS AND MECHANISMS OF HYPOCHLOROUS ACID REACTIONS

Hypochlorous acid (HOCI) is a strong oxidant formed in neutrophils by the myeloperoxidase-catalyzed oxidation of chloride. Using stopped-how with spectrophotometric detection, HOCI was found to react very rapidly with glutathione and ascorbate and less rapidly with taurine. No evidence could be found for the formation of reactive free-radical intermediates in these reactions, in support of an electrophilic mechanism. In contrast, the reaction with iron(II) aquo or citrate complexes (k similar to 10(4) dm(3) mol(-1) s(-1) in acidic solution) yielded reactive intermediates distinguishable from hydroxyl radicals. The reaction between HOCI and ferrous ions, which is analogous to but faster than the Fenton reaction, is a potential source of free radicals in activated neutrophils. (C) 1995 Academic Press, Inc.