EQUILIBRIUM-CONSTANTS FOR THIOL DISULFIDE INTERCHANGE REACTIONS - A COHERENT, CORRECTED SET

Equilibrium constants (K(eq)) for the thiol-disulfide interchange reactions between dithiothreitol (DTT) and lipoic acid (14.2 +/- 0.7), lipoic acid (Lip) and mercaptoethanol (13.3 M +/- 1.0 M), and mercaptoethanol (ME) and glutathione (GSH or GSSG) (1.20 +/- 0.10) were measured in D2O at pD 7.0 by H-1 NMR spectroscopy. Two of these equilibrium constants [DTT and Lip (21.3 +/- 0.9), and Lip and ME (8.6 +/- 0.7)] were also measured in D2O/CD3OD. These values are compared with those obtained by other methods. A coherent set of values for the equilibrium constants between DTT or ME and thiols having a range of structures was assembled (Table III). The recommended value for the equilibrium constant between DTT and GSH is 210 M (K(eq) = [DTT(ox)][GSH]2/([DTT(red)][GSSG])).