Hydrolyzes ITP and dITP to their respective monophosphate derivatives. Xanthosine 5'-triphosphate (XTP) is also a potential substrate. May be the major enzyme responsible for regulating ITP concentration in cells.
Ubiquitous. Highly expressed in heart, liver, sex glands, thyroid and adrenal gland.
Defects in ITPA are the cause of inosine triphosphate pyrophosphohydrolase deficiency (ITPA deficiency) [MIM:147520]. It is a common inherited trait characterized by the abnormal accumulation of inosine triphosphate (ITP) in erythrocytes and also leukocytes and fibroblasts. The pathological consequences of ITPA deficiency, if any, are unknown. However, it might have pharmacogenomic implications and be related to increased drug toxicity of purine analog drugs. 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.