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001-es BibID:BIBFORM062162
035-os BibID:(WoS)000351483700013 (Scopus)84925484963
Első szerző:Vasas Anita (környezetkutató)
Cím:Kinetic and thermodynamic studies on the disulfide-bond reducing potential of hydrogen sulfide / Anita Vasas, Éva Dóka, István Fábián, Péter Nagy
Megjegyzések:The significance of persulfide species in hydrogen sulfide biology is increasingly recognized. However,the molecular mechanisms of their formation remain largely elusive. The obvious pathway of the reduction of biologically abundant disulfide moieties by sulfide was challenged on both thermodynamicand kinetic grounds. Using DTNB (5,5·-dithiobis-(2-nitrobenzoic acid), also known as Ellman's reagent)as a model disulfide we conducted a comprehensive kinetic study for its reaction with sulfide. The bimolecular reaction is relatively fast with a second-order rate constant of 889 ? 12 M?1s?1 at pH = 7.4. pHdependence of the rate law revealed that the reaction proceeds via the bisulfide anion species with aninitial nucleophilic thiol-disulfide exchange reaction to give 5-thio-2-nitrobenzoic acid (TNB) and TNBpersulfide with a pH independent second-order rate constant of 1090 ? 12 M?1s?1. However, kinetic studiesand stoichiometric analyses in a wide range of reactant ratios together with kinetic simulations revealed that it is a multistep process that proceeds via kinetically driven, practically irreversible reactionsalong the disulfide ? persulfide ? inorganic polysulfides axis. The kinetic model postulated here, whichis fully consistent with the experimental data, suggests that the TNB-persulfide is further reduced bysulfide with a second-order rate constant in the range of 5 ? 103 ? 5 ? 104 M?1s?1 at pH 7.4 and eventually yields inorganic polysulfides and TNB. The reactions of cystine and GSSG with sulfide were foundto be significantly slower and to occur via more complicated reaction schemes. 1H NMR studies suggestthat these reactions also generate Cys-persulfide and inorganic polysulfide species, but in contrast withDTNB, in consecutive equilibrium processes that are sensitive to changes in the reactant and productratios. Collectively, our results demonstrate that the reaction of disulfides with sulfide is a highly systemspecific process from both thermodynamic and kinetic aspects, which together with the considerablesteady-state concentrations of the reactants in biological systems signifies physiological relevance.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Hydrogen sulfide
Disulfide reduction
Kinetics and mechanisms
Megjelenés:Nitric Oxide-Biology And Chemistry. - 46 (2015), p. 93-101. -
További szerzők:Dóka Éva (1988-) (vegyész) Fábián István (1956-) (vegyész) Nagy Péter (1976-) (vegyész)
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