摘要：We have purified bovine brain Zn2+-dependent acid phosphatase (Zn2+-APase), which requires Zn2+ ions to hydrolyze the substrate p-nitrophenyl phosphate (pNPP) in an acidic environment. The substrate specificity and metal requirement of Zn2+-APase at a physiological pH was also studied. The enzyme exhibited hydrolytic activity on myo-inositol-1-and-2-monophosphates, 2'-adenosine monophosphate, 2'-guanosine monophosphate, and the α- and β-glycerophosphates, glucose-1-phosphate, and fructose-6-phosphate in 50 mM Tris-HCl buffer (pH 7.4) in the presence of Mg2+ ions, but not on pNPP and phosphotyrosine. Zn2+, Mn2+ and Co2+ ions were less effective for activation. Among the above substrates, myo-inositol-1-phosphate was the most susceptible to hydrolysis by the enzyme in the presence of Mg2+ ions. The enzyme exhibited an optimum pH at around 8 for myo-inositol-1-phosphate in the presence of 3 mM Mg2+ ions. The Mg2+-dependent myo-inositol-1-phosphatase activity of the enzyme was significantly inhibited by Li+ ions. The Zn2+-dependent p-nitrophenyl phosphatase activity and Mg2+-dependent myo-inositol-1-phosphatase activity of the purified enzyme fraction exhibited similar behavior on Sephadex G-100 and Mono Q colomns. These findings suggest that Zn2+-APase also exhibits Mg2+-dependent myo-inositol-1-phosphatase activity under physiological conditions.
