Erythrocyte gamma-glutamylcysteine synthetase from normal and low-glutathione sheep.

gamma-Glutamylcysteine synthetase (L-glutamate:L-cysteine gamma-ligase (ADP-forming), EC 6.3.2.2) was purified from the erythrocytes of normal and low-glutathione sheep. The molecular weight (78 000), pH optimum (pH 7), substrate specificity, inhibition constant for glutathione (0.44-0.50 mM), electrophoretic mobility, and heat stability were similar for the purified enzyme from both sources. Using immunological techniques, the specific activity of gamma-glutamylcysteine synthetase from low-glutathione sheep was lower than that from normal sheep.