Abstract

Acrolein, a genotoxic aldehyde released in the metabolic activation of the cytostatic drug cyclophosphamide, is inactivated by glutathione transferases either by conjugation with reduced glutathione or by covalent binding to the enzymes in the absence of glutathione. The catalytic efficiency (kcat/Km) with acrolein as a substrate was determined for representatives of the three classes Alpha, Mu, and Pi of human glutathione transferases. Transferase pi exhibited the highest and transferase epsilon the lowest catalytic efficiencies, respectively. As measured by the kcat/Km value, acrolein ranks among the most active substrates known for transferase pi. The irreversible binding of acrolein to the enzymes was monitored as the inactivation of the enzyme activity. Transferase pi reacted significantly more rapidly with acrolein than did transferases mu and epsilon.