The initial metabolism of 6-mercaptopurine occurs along the competing routes catalyzed by thiopurine methyltransferase (TPMT), xanthine oxidase (XO), and hypoxanthine phosphoribosyltransferase (HPRT). Further metabolism of the thionucleotide is catalyzed by inosine monophosphate dehydrogenase (IMPDH) and guanosine monophosphate synthetase (GMPS). The diphosphates and triphosphates are formed by their respective monophosphate (MPK) and diphosphate (DPK) kinases.
Reproduced with permission from: Cuffari C, et al. Gut 1996; 39:401. Copyright 1996 BMJ Publishing Group.
