Protection of chymotrypsin from inactivation by a N-mustard analog

Chymotrypsin activity is rapidly inactivated by the N-mustard anti-tumor drug, chlorambucil. Since mustards react with thiols, amines, carboxyls, imidazoles, and sulfide sites on proteins, N-acetylcysteine, 2 proprietary protein hydrolyzates, beta-mercaptoethanol, ethanolamine, and sodium lactate were tested for their capacity to protect chymotrypsin from inactivation by the mustard. In each instance, protection was afforded to chymotrypsin. In as much as N-acetylcysteine protected chymotrypsin from inactivation by chlorambucil, it is suggested that this thiol compound may serve as a detoxication agent and may not require prior transformation into glutathione by cells in order to reduce mustard levels within the cells, as suggested by Smith and Gross (Proceedings of the NATO Panel VIII meeting, Grenoble, France, 1991.) It is further suggested that amino acids present as biosynthetic and degradative components of cells may detoxify mustards.