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MGP001682

UniProt Annotations

Entry Information
Gene Nameinosine triphosphatase (nucleoside triphosphate pyrophosphatase)
Protein EntryITPA_HUMAN
UniProt IDQ9BY32
SpeciesHuman
Comments
Comment typeDescription
Alternative ProductsEvent=Alternative splicing; Named isoforms=3; Name=1; IsoId=Q9BY32-1; Sequence=Displayed; Name=2; IsoId=Q9BY32-2; Sequence=VSP_042548; Note=No experimental confirmation available.; Name=3; IsoId=Q9BY32-3; Sequence=VSP_045545; Note=No experimental confirmation available.;
Biophysicochemical PropertiesKinetic parameters: KM=0.51 mM for ITP {ECO:0000269|PubMed:11278832, ECO:0000269|PubMed:17090528}; KM=0.31 mM for dITP {ECO:0000269|PubMed:11278832, ECO:0000269|PubMed:17090528}; KM=0.57 mM for XTP {ECO:0000269|PubMed:11278832, ECO:0000269|PubMed:17090528}; KM=40.7 uM for dHAPTP {ECO:0000269|PubMed:11278832, ECO:0000269|PubMed:17090528}; KM=933 uM for dGTP {ECO:0000269|PubMed:11278832, ECO:0000269|PubMed:17090528}; Vmax=1520 umol/min/mg enzyme for ITP {ECO:0000269|PubMed:11278832, ECO:0000269|PubMed:17090528}; Vmax=940 umol/min/mg enzyme for dITP {ECO:0000269|PubMed:11278832, ECO:0000269|PubMed:17090528}; Vmax=1680 umol/min/mg enzyme for XTP {ECO:0000269|PubMed:11278832, ECO:0000269|PubMed:17090528}; Note=Vmax values are similar for dITP, dHAPTP and dGTP.; pH dependence: Optimum pH is 10. {ECO:0000269|PubMed:11278832, ECO:0000269|PubMed:17090528};
Catalytic ActivityA nucleoside triphosphate + H(2)O = a nucleotide + diphosphate. {ECO:0000255|HAMAP-Rule:MF_03148}.
CofactorName=Mg(2+); Xref=ChEBI:CHEBI:18420; Evidence={ECO:0000269|PubMed:17138556}; Note=Binds 1 Mg(2+) ion per subunit. {ECO:0000269|PubMed:17138556};
DiseaseInosine triphosphate pyrophosphohydrolase deficiency (ITPAD) [MIM:613850]: A common inherited condition characterized by the abnormal accumulation of inosine triphosphate in erythrocytes. It might have pharmacogenomic implications and be related to increased drug toxicity of purine analog drugs. {ECO:0000269|PubMed:12384777, ECO:0000269|PubMed:12436200, ECO:0000269|Ref.2}. Note=The disease is caused by mutations affecting the gene represented in this entry. Three different human populations have been reported with respect to their ITPase activity: high, mean (25% of high) and low activity. The variant Thr-32 is associated with complete loss of enzyme activity, may be by altering the local secondary structure of the protein. Heterozygotes for this polymorphism have 22.5% of the control activity: this is consistent with a dimeric structure of the enzyme.
FunctionPyrophosphatase that hydrolyzes the non-canonical purine nucleotides inosine triphosphate (ITP), deoxyinosine triphosphate (dITP) as well as 2'-deoxy-N-6-hydroxylaminopurine triposphate (dHAPTP) and xanthosine 5'-triphosphate (XTP) to their respective monophosphate derivatives. The enzyme does not distinguish between the deoxy- and ribose forms. Probably excludes non-canonical purines from RNA and DNA precursor pools, thus preventing their incorporation into RNA and DNA and avoiding chromosomal lesions. {ECO:0000255|HAMAP-Rule:MF_03148, ECO:0000269|PubMed:17090528}.
SimilarityBelongs to the HAM1 NTPase family. {ECO:0000255|HAMAP- Rule:MF_03148}.
Subcellular LocationCytoplasm {ECO:0000255|HAMAP-Rule:MF_03148, ECO:0000269|PubMed:11278832}.
SubunitHomodimer. {ECO:0000255|HAMAP-Rule:MF_03148, ECO:0000269|PubMed:11278832, ECO:0000269|PubMed:17138556}.
Tissue SpecificityUbiquitous. Highly expressed in heart, liver, sex glands, thyroid and adrenal gland.
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