Biology:ITPA

Short description: Protein-coding gene in the species Homo sapiens

Generic protein structure example

Inosine triphosphate pyrophosphatase is an enzyme that in humans is encoded by the ITPA gene, by the rdgB gene in bacteria E.coli and the HAM1 gene in yeast S. cerevisiae; the protein is also encoded by some RNA viruses of the Potyviridae family. Two transcript variants encoding two different isoforms have been found for this gene. Also, at least two other transcript variants have been identified which are probably regulatory rather than protein-coding.

Function

The protein encoded by this gene hydrolyzes inosine triphosphate and deoxyinosine triphosphate to the monophosphate nucleotide and diphosphate. The enzyme possesses a multiple substrate-specificity and acts on other nucleotides including xanthosine triphosphate and deoxyxanthosine triphosphate. The encoded protein, which is a member of the HAM1 NTPase protein family, is found in the cytoplasm and acts as a homodimer.

Clinical significance

Defects in the encoded protein can result in inosine triphosphate pyrophosphorylase deficiency. The enzyme ITPase dephosphorylates ribavirin triphosphate in vitro to ribavirin monophosphate, and ITPase reduced enzymatic activity present in 30 % of humans potentiates mutagenesis in hepatitis C virus. Gene variants predicting reduced predicted ITPase activity have been associated with decreased risk of ribavirin-induced anemia, increased risk of thrombocytopenia, lower ribavirin concentrations, as well as a ribavirin-like reduced relapse risk following interferon-based therapy for hepatitis C virus (HCV) genotype 2 or 3 infection.

Reading

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• Fraser JH; Meyers H; Henderson JF et al. (1976). "Individual variation in inosine triphosphate accumulation in human erythrocytes". Clin. Biochem. 8 (6): 353–64. doi:10.1016/S0009-9120(75)93685-1. PMID 1204209. 
• Clawson GA; Song YL; Schwartz AM et al. (1992). "Interaction of human immunodeficiency virus type I Rev protein with nuclear scaffold nucleoside triphosphatase activity". Cell Growth Differ. 2 (11): 575–82. PMID 1667585. 
• Deloukas P; Matthews LH; Ashurst J et al. (2002). "The DNA sequence and comparative analysis of human chromosome 20". Nature 414 (6866): 865–71. doi:10.1038/414865a. PMID 11780052. Bibcode: 2001Natur.414..865D. 
• Sumi S; Marinaki AM; Arenas M et al. (2002). "Genetic basis of inosine triphosphate pyrophosphohydrolase deficiency". Hum. Genet. 111 (4–5): 360–7. doi:10.1007/s00439-002-0798-z. PMID 12384777. 
• "DNA polymorphisms in ITPA including basis of inosine triphosphatase deficiency". J. Hum. Genet. 47 (11): 620–2. 2003. doi:10.1007/s100380200095. PMID 12436200. 
• Strausberg RL; Feingold EA; Grouse LH et al. (2003). "Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences". Proc. Natl. Acad. Sci. U.S.A. 99 (26): 16899–903. doi:10.1073/pnas.242603899. PMID 12477932. Bibcode: 2002PNAS...9916899M. 
• Gerhard DS; Wagner L; Feingold EA et al. (2004). "The Status, Quality, and Expansion of the NIH Full-Length cDNA Project: The Mammalian Gene Collection (MGC)". Genome Res. 14 (10B): 2121–7. doi:10.1101/gr.2596504. PMID 15489334. 
• Marinaki AM; Duley JA; Arenas M et al. (2005). "Mutation in the ITPA gene predicts intolerance to azathioprine". Nucleosides Nucleotides Nucleic Acids 23 (8–9): 1393–7. doi:10.1081/NCN-200027639. PMID 15571265. 
• Marinaki AM; Sumi S; Arenas M et al. (2005). "Allele frequency of inosine triphosphate pyrophosphatase gene polymorphisms in a Japanese population". Nucleosides Nucleotides Nucleic Acids 23 (8–9): 1399–401. doi:10.1081/NCN-200027641. PMID 15571266. 
• Maeda T; Sumi S; Ueta A et al. (2005). "Genetic basis of inosine triphosphate pyrophosphohydrolase deficiency in the Japanese population". Mol. Genet. Metab. 85 (4): 271–9. doi:10.1016/j.ymgme.2005.03.011. PMID 15946879. 
• "Pharmacogenetic association with adverse drug reactions to azathioprine immunosuppressive therapy following liver transplantation". Liver Transpl. 11 (7): 826–33. 2005. doi:10.1002/lt.20377. PMID 15973722. 
• Porta J; Kolar C; Kozmin SG et al. (2006). "Structure of the orthorhombic form of human inosine triphosphate pyrophosphatase". Acta Crystallographica Section F 62 (Pt 11): 1076–81. doi:10.1107/S1744309106041790. PMID 17077483. 
• Arenas M; Duley J; Sumi S et al. (2007). "The ITPA c.94C>A and g.IVS2+21A>C sequence variants contribute to missplicing of the ITPA gene". Biochim. Biophys. Acta 1772 (1): 96–102. doi:10.1016/j.bbadis.2006.10.006. PMID 17113761. 
• Stenmark P; Kursula P; Flodin S et al. (2007). "Crystal structure of human inosine triphosphatase. Substrate binding and implication of the inosine triphosphatase deficiency mutation P32T". J. Biol. Chem. 282 (5): 3182–7. doi:10.1074/jbc.M609838200. PMID 17138556. 
• Atanasova S; Shipkova M; Svinarov D et al. (2007). "Analysis of ITPA phenotype-genotype correlation in the Bulgarian population revealed a novel gene variant in exon 6". Therapeutic Drug Monitoring 29 (1): 6–10. doi:10.1097/FTD.0b013e3180308554. PMID 17304144.