Nitroso Group Transfer in S -Nitrosocysteine: Evidence of a New Decomposition Pathway for Nitrosothiols

The rate of S-nitrosocysteine decomposition in a pH range between 0.7 S-nitrosocysteine, which proceeds via an intramolecular nitroso group transfer producing a primary N-nitrosamine that decomposes rapidly to give the corresponding diazonium salt. The nitroso group transfer reaction occurs intermolecularly for the decomposition pathway exhibiting a quadratic dependence on cysteine concentration. Both nitroso group transfer pathways are subject to acid catalysis by cysteine. Kinetic results indicate that the extent of S‚‚‚NO bond cleavage in the transition state is ahead of protonation of the AH‚‚‚S sulfur atom. The results obtained show the existence of a new decomposition pathway for the S-nitrosocysteine where NO is not released, and hence, it has a significant biological impact due to the potential use of nitrosothiols as NO donors. Fil: Adam, Claudia Guadalupe. Universidad Nacional del Litoral. Facultad de Ingeniería Química; Argentina. Universidad de Santiago de Compostela; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: García Río, Luis. Universidad de Santiago de Compostela; EspañaFil: Leis, José Ramón. Universidad de Santiago de Compostela; EspañaFil: Ribeiro, Lara. Universidad de Santiago de Compostela; Españ