Fig. 1.

Thiopurine metabolism and transportation. Drugs are shown in gray boxes: AZA azathioprine, 6-MP 6-mercaptopurine. Metabolites are shown in white boxes: 6-MMP 6-Methylmercaptopurine, 8-OHMP 8-hydroxy-6-mercaptopurine, 6-TUA 6-thiouric acid, 6-MMPR 6-methylmercaptopurine ribonucleotides, 6-TIMP 6-thioinosine monophosphate, 6-TIDP 6-thioinosine diphosphate, 6-TITP 6-thioinosine triphosphate, 6-TXMP 6-thioxanthosine monophosphate, 6-TGMP 6-thioguanine monophosphate, 6-TGDP 6-thioguanine diphosphate, 6-TGTP 6-thioguanine triphosphate, 6-TdGMP 6-thio-deoxyguanine monophosphate, 6-TdGDP 6-thio-deoxyguanine diphosphate, 6-TdGTP 6-thio-deoxyguanine triphosphate, 6-MTGMP 6-methylthioguanine monophosphate, 6-TGN 6-thioguaninenucleotides. Enzymes or transporters are shown in black boxes: XO xanthine oxidase, TPMT thiopurine S-methyl transferase, HGPRT hypoxanthine phosphoribosyl transferase, IMPDH inosine monophosphate dehydrogenase, GMPS guanosine monophosphate synthetase, MPK monophosphate kinase, DPK diphosphate kinase, ITPase inosine triphosphate pyrophosphatase, MRP4 multidrug resistance-associated protein 4