The anti-cancer drug chlorambucil as a substrate for the human polymorphic enzyme glutathione transferase P1-1: kinetic properties and crystallographic characterisation of allelic variants.

摘要: The commonly used anti-cancer drug chlorambucil is the primary treatment for patients with chronic lymphocytic leukaemia. Chlorambucil has been shown to be detoxified by human glutathione transferase Pi (GST P1-1), an enzyme that often found over-expressed in cancer tissues. allelic variants of GST P1-1 are associated differing susceptibilities leukaemia and differ markedly their efficiency catalysing (GSH) conjugation reactions. Here, we perform detailed kinetic studies aid three representative co-substrates. We show catalytic properties highly substrate-dependent. also all exhibit same temperature stability range 10 degrees C 45 C. have determined crystal structures complex its GSH conjugate two these different residues at positions 104 113. bind a non-productive mode substrate-binding site (H-site) absence GSH. This result suggests under certain stress conditions where levels low, can inactivate sequestering it from surrounding medium. However, presence GSH, binds H-site productive undergoes reaction present crystal. structure GSH-chlorambucil bound *C variant identical *A ruling out hypothesis differences between cause structural changes active site. Finally, very poor inhibitor contrast ethacrynic acid, which similar fashion but act as both substrate inhibitor.