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Pathway Description
Thioguanine Action Pathway (old)
Homo sapiens
Drug Action Pathway
Thioguanine is a purine antimetabolite prodrug closely related to mercaptopurine and similarly inhibits purine metabolism. The thioguanine pathway is shown as a part of the mercaptopurine pathway. Thioguanine exerts cytotoxic effects via incorporation of thiodeoxyguanosine triphosphate into DNA and thioguanosine triphosphate into RNA and inhibition of Ras-related C3 botulinum toxin substrate 1, which induces apoptosis of activated T cells. Once in a cell, thioguanine is converted to thioguanosine monophosphate by hypoxanthine-guanine phosphoribosyltransferase. Thioguanosine monophosphate is then phosphorylated to thioguanosine diphosphate, which is converted via a thiodeoxyguanosine diphosphate intermediate to thiodeoxyguanosine triphosphate. Thiodeoxyguanosine triphosphate is incorporated into DNA causing cytotoxicity. Thioguanosine diphosphate is also converted to thioguanosine triphosphate which is incorporated into RNA. The thioguanosine triphosphate metabolite also inhibits Ras-related C3 botulinum toxin substrate 1, a plasma membrane-associated small GTPase that regulates cellular processes, inducing apoptosis in activated T cells.
References
Thioguanine Pathway (old) References
Nelson, D.L., & Cox, M.M. Lehninger Principles of Biochemistry (3rd ed.) (2000). New York: Worth Publishers.
Sahasranaman S, Howard D, Roy S: Clinical pharmacology and pharmacogenetics of thiopurines. Eur J Clin Pharmacol. 2008 Aug;64(8):753-67. doi: 10.1007/s00228-008-0478-6. Epub 2008 May 28.
Pubmed: 18506437
Stocco G, Cheok MH, Crews KR, Dervieux T, French D, Pei D, Yang W, Cheng C, Pui CH, Relling MV, Evans WE: Genetic polymorphism of inosine triphosphate pyrophosphatase is a determinant of mercaptopurine metabolism and toxicity during treatment for acute lymphoblastic leukemia. Clin Pharmacol Ther. 2009 Feb;85(2):164-72. doi: 10.1038/clpt.2008.154. Epub 2008 Aug 6.
Pubmed: 18685564
Mercaptopurine Pathway References
Nelson, D.L., & Cox, M.M. Lehninger Principles of Biochemistry (3rd ed.) (2000). New York: Worth Publishers.
Sahasranaman S, Howard D, Roy S: Clinical pharmacology and pharmacogenetics of thiopurines. Eur J Clin Pharmacol. 2008 Aug;64(8):753-67. doi: 10.1007/s00228-008-0478-6. Epub 2008 May 28.
Pubmed: 18506437
Stocco G, Cheok MH, Crews KR, Dervieux T, French D, Pei D, Yang W, Cheng C, Pui CH, Relling MV, Evans WE: Genetic polymorphism of inosine triphosphate pyrophosphatase is a determinant of mercaptopurine metabolism and toxicity during treatment for acute lymphoblastic leukemia. Clin Pharmacol Ther. 2009 Feb;85(2):164-72. doi: 10.1038/clpt.2008.154. Epub 2008 Aug 6.
Pubmed: 18685564
Purine Metabolism References
Lehninger, A.L. Lehninger principles of biochemistry (4th ed.) (2005). New York: W.H Freeman.
Salway, J.G. Metabolism at a glance (3rd ed.) (2004). Alden, Mass.: Blackwell Pub.
Garcia-Gil M, Camici M, Allegrini S, Pesi R, Petrotto E, Tozzi MG: Emerging Role of Purine Metabolizing Enzymes in Brain Function and Tumors. Int J Mol Sci. 2018 Nov 14;19(11). pii: ijms19113598. doi: 10.3390/ijms19113598.
Pubmed: 30441833
Davies O, Mendes P, Smallbone K, Malys N: Characterisation of multiple substrate-specific (d)ITP/(d)XTPase and modelling of deaminated purine nucleotide metabolism. BMB Rep. 2012 Apr;45(4):259-64.
Pubmed: 22531138
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