Any substance that inhibits glutamate-cysteine ligase (gamma-glutamylcysteine synthetase), an enzyme that catalyzes the ATP-dependent condensation of cysteine and glutamate to form the dipeptide gamma-glutamylcysteine, the rate-limiting step in the biosynthesis of glutathione. Since glutathione is critical in protecting cells against oxidative stress, its depletion results in free radical-induced apoptosis.