Oxidation of Bromide by the Human Leukocyte Enzymes Myeloperoxidase and Eosinophil Peroxidase: FORMATION OF BROMAMINES (∗)

摘要: Myeloperoxidase and eosinophil peroxidase catalyzed the oxidation of bromide ion by hydrogen peroxide (H2O2) produced a brominating agent that reacted with amine compounds to form bromamines, which are long-lived oxidants containing covalent nitrogen-bromine bonds. Results were consistent an equilibrium mixture hypobromous acid (HOBr) hypobromite (OBr-). Up 1 mol bromamine was per mole H2O2, indicating formation prevented reduction HOBr/OBr- H2O2 loss oxidizing activity. Bromamines differed from in bromamines slowly not reduced dimethyl sulfoxide, had absorption spectra similar those chloramines, but shifted 36 nm toward higher wavelengths. Mono- di-bromo derivatives (RNHBr RNHBr2) βamino taurine relatively stable half-lives 70 16 h at pH 7, 37°C. The mono-bromamine obtained 200-fold excess over amount di-bromamine 2:1 ratio amine. In presence physiologic levels both (0.1 mM) chloride M), myeloperoxidase mixtures chloramines 6 ± 4% 88 bromamine. contrast, only mono-chloramine derivative (RNHCl) formed when hypochlorous (HOCl) hypochlorite (OCl-) added solutions rapid chloramine HOCl/OCl-, did react within results indicate enzyme-catalyzed or took place compound 10 mM higher, secondary reactions such as HOCl/OCl- exchange chlorine atoms chloramines. Therefore, equal oxidized enzyme. Bromide preferred substrate for enzymes.