Cloning, Expression, and Characterization of a Human Inosine Triphosphate Pyrophosphatase Encoded by the ITPA Gene

Shengrong Lin, Alexander G. McLennan, Kang Ying, Zhao Wang, Shaohua Gu, Hua Jin, Chaoqun Wu, Weiping Liu, Youzhong Yuan, Rong Tang, Yi Xie, Yumin Mao

Research output: Contribution to journalArticlepeer-review

106 Scopus citations

Abstract

ITP and dITP exist in all cells. dITP is potentially mutagenic, and the levels of these nucleotides are controlled by inosine triphosphate pyrophosphatase (EC 3.6.1.19). Here we report the cloning, expression, and characterization of a 21.5-kDa human inosine triphosphate pyrophosphatase (hITPase), an enzyme whose activity has been reported in many animal tissues and studied in populations but whose protein sequence has not been determined before. At the optimal pH of 10.0, recombinant hITPase hydrolyzed ITP, dITP, and xanthosine 5′-triphosphate to their respective monophosphates whereas activity with other nucleoside triphosphates was low. Km values for ITP, dITP, and xanthosine 5′-triphosphate were 0.51, 0.31, and 0.57 mM, respectively, and kcat values were 580, 360, and 640 s-1, respectively. A divalent cation was absolutely required for activity. The gene encoding the hITPase cDNA sequence was localized by radiation hybrid mapping to chromosome 20p in the interval D20S113-D20S97, the same interval in which the ITPA inosine triphosphatase gene was previously localized. A BLAST search revealed the existence of many similar sequences in organisms ranging from bacteria to mammals. The function of this ubiquitous protein family is proposed to be the elimination of minor potentially mutagenic or clastogenic purine nucleoside triphosphates from the cell.

Original languageEnglish (US)
Pages (from-to)18695-18701
Number of pages7
JournalJournal of Biological Chemistry
Volume276
Issue number22
DOIs
StatePublished - Jun 1 2001
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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