Insights into the mechanism of the reaction between hydrogen sulfide and peroxynitrite

E. CUEVASANTA; A. ZEIDA; S. CARBALLAL; R. WEDMANN; U.N. MORZAN; M. TRUJILLO; R. RADI; D.A. ESTRIN; M.R. FILIPOVIC; B. ALVAREZ

FREE RADICAL BIOLOGY AND MEDICINE

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2015 vol. 80 p. 93 - 100

0891-5849

Hydrogen sulfide and peroxynitrite are endogenously generated molecules that participate in biologi-cally relevant pathways. A revision of the kinetic features of the reaction between peroxynitrite andhydrogen sulfide revealed a complex process. The rate constant of peroxynitrite decay, (6.65 7 0.08) Â10 3 M À 1 s À 1 in 0.05 M sodium phosphate buffer (pH 7.4, 37 1C), was affected by the concentration ofbuffer. Theoretical modeling suggested that, as in the case of thiols, the reaction is initiated by thenucleophilic attack of HS À on the peroxide group of ONOOH by a typical bimolecular nucleophilicsubstitution, yielding HSOH and NO 2 À . In contrast to thiols, the reaction then proceeds to the formationof distinct products that absorb near 408 nm. Experiments in the presence of scavengers and carbondioxide showed that free radicals are unlikely to be involved in the formation of these products. Theresults are consistent with product formation involving the reactive intermediate HSSH and its fastreaction with a second peroxynitrite molecule. Mass spectrometry and UV?Vis absorption spectrapredictions suggest that at least one of the products is HSNO 2 or its isomer HSONO.