- A spectrophotometric assay of gamma-glutamylcysteine synthetase and glutathione synthetase in crude extracts from tissues and cultured mammalian cells. Volohonsky, G., Tuby, C.N., Porat, N., Wellman-Rousseau, M., Visvikis, A., Leroy, P., Rashi, S., Steinberg, P., Stark, A.A. Chem. Biol. Interact. (2002)