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Kinetics of nitrosation of GSH using NO donors
Author(s) -
Madrasi Kumpal Jagdish,
Joshi Mahesh S,
Tsoukias Nikolaos
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.984.22
Subject(s) - nitrosation , chemistry , glutathione , kinetics , reaction rate constant , nitrite , nitric oxide , medicinal chemistry , biochemistry , biophysics , enzyme , organic chemistry , nitrate , biology , physics , quantum mechanics
Modification of critical thiols by reactive nitrogen species (RNS) act as regulators of protein mediated signaling. Nitrosothiols are also believed to act as vasodilators which can release NO and activate the heme protein guanylate cyclase, thus initiating the mechanism for vasodilation. Nitrosation is thought to be mediated by dinitrogen trioxide (N 2 O 3 ). Combination of NO with thiyl radical (GS.) following oxidation of the thiyl anion by NO 2 has also been suggested as a mechanism for nitrosothiol formation. We investigate the kinetic mechanism of GSH (0–20mM) nitrosation in vitro by NO donor PAPA/NO (0.5 – 10 mM). GSNO formation was assessed spectrophotometrically at 338 nm. Results suggest a Michaelis‐Menten dependence of the rate on GSH concentration with a half‐maximum constant (K m,GSH ) that depends on NO concentration. If there were solely one mechanism of nitrosation, one would expect a constant K m GSH value. Increasing [NO] up to 10 fold showed a proportional increase in K m,GSH . Pseudo steady state approximation yields the following kinetic rate for GS mediated nitrosation: d d t [ G S N O ] = k 1 [ O 2 ] [ N O ] 2 [ [ G S H ] k 2 [ N O ] + [ G S H ] ]The reported increase in K m,GSH with NO concentration suggest a significant contribution of GS.mediated nitrosation in the formation of GSNO. (Supported by NIH SC1HL95101)