Redox buffering of hypochlorous acid by thiocyanate in physiologic fluids.

The major antimicrobial products of neutrophilic myeloperoxidase (MPO) in physiologic fluids are hypochlorous acid (HOCl) and hypothiocyanite (OSCN-), and the former is generally believed to be the killing agent. However, we have determined that HOCl oxidizes SCN- in a facile nonenzymic reaction. The observed kinetics and computational models substantiate the hypothesis that SCN- serves to moderate the potential autotoxicity of HOCl by restricting its lifetime in physiologic fluids.