Purification and properties of human erythrocyte inosine triphosphate pyrophosphohydrolase

Inosine triphosphate pyrophosphohydrolase from human erythrocytes was purified and characterized. The enzyme is highly specific for ITP and shows optimal activity in glycine buffer pH 9.6 and 50 mM MgCl2. The Km of the enzyme is 1.3 × 10−4, the Vmax = 1.2 × 10−9 and the Keq = 3.8 × 104. Human erythrocyte ITP pyrophosphohydrolase does not require SH compounds for activation. The enzyme is inhibited by Cd++, Co++, and Ca++ ions and by phydroxymercuribenzoate.