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Kinetics and equilibria of S ‐nitrosothiol—thiol exchange between glutathione, cysteine, penicillamines and serum albumin
Author(s) -
Meyer David J.,
Kramer Harry,
Özer Nazmi,
Coles Brian,
Ketterer Brian
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)00429-3
Subject(s) - glutathione , cysteine , chemistry , thiol , kinetics , penicillamine , albumin , s nitrosoglutathione , reaction rate constant , medicinal chemistry , stereochemistry , biochemistry , enzyme , organic chemistry , physics , quantum mechanics
The kinetics and equilibria of S ‐nitrosothiol‐thiol (SNO—SH) exchange reactions were determined using differential optical absorption. At pH 7.4 and 37°C, k 2 values ranged from 0.9 M −1 · s −1 for the reaction between S ‐nitroso‐glutathione (GSNO) and N ‐acetyl‐penicillamine, and up to 279 M −1 · s −1 for the exchange between S ‐nitroso‐penicillamine (penSNO) and GSH. SNO—SH exchange involving GSH/GSNO and cysteine/cySNO was relatively rapid, k 2 approx. 80 M −1 · s −1 with an equilibrium constant slightly in favour of GSNO. GSNO was strongly favoured in equilibrium with penSNO, k eq 0.0039. In the case of SNO—SH exchange between S ‐nitroso human serum albumin (albSNO) and GSH or cysteine k 2 values were 3.2 and 9.1 M −1 · s −1 , respectively. The results show that the initial rate of SNO—SH exchange between physiological albSNO (7 μM) and venous plasma levels of GSH and cysteine is very slow, < 1%/min. On the other hand, if a nitrosothiol such as cySNO were to enter a cell, it would be rapidly converted to GSNO (43%/s).