Participation of the Unsymmetrical Disulfide of Coenzyme A and Glutathione in an Enzymatic Sulfhydryl-Disulfide Interchange

Abstract An enzyme that catalyzes the following sulfhydryl-disulfide interchange reaction has been purified 180-fold from bovine kidney. GSH + CoASSG ⇌ GSSG + CoA-SH In addition, it has been detected in most rat tissues studied. Its pH optimum is 8.2 and the equilibrium constant for the reaction is near unity at pH 6.9 and 25°. Michaelis constants for reduced glutathione and CoASSG are 3.3 x 10-4 m and 4.5 x 10-5 m, respectively. The molecular weight of the enzyme, determined by gel filtration, is approximately 12,000. Several unsymmetrical disulfides containing a glutathione residue are equally as effective as substrates. The enzyme, which becomes less active during storage, is largely reactivated by GSH. Its potential physiological significance is discussed.