Zinc-ion-dependent acid phosphatase exhibits magnesium-ion-dependent myo-inositol-1-phosphatase activity.
We have purified bovine brain Zn(2+)-dependent acid phosphatase (Zn(2+)-APase), which requires Zn2+ ions to hydrolyze the substrate p-nitrophenyl phosphate (pNPP) in an acidic environment. The substrate specificity and metal requirement of Zn(2+)-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 alpha- and beta-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 3 mM 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 Mg(2+)-dependent myo-inositol-1-phosphatase activity of the enzyme was significantly inhibited by Li+ ions. The Zn(2+)-dependent p-nitrophenyl phosphatase activity and Mg(2+)-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 Zn(2+)-APase also exhibits Mg(2+)-dependent myo-inositol-1-phosphatase activity under physiological conditions.
Fujimoto
S
S
Department of Environmental Biochemistry, Kyoto Pharmaceutical University, Japan.
Okano
I
I
Tanaka
Y
Y
Sumida
Y
Y
Tsuda
J
J
Kawakami
N
N
Shimohama
S
S
D000135:Acid Phosphatase / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007295:Inositol Phosphates / Q000737:chemistry; D008274:Magnesium / Q000378:metabolism; D009596:Nitrophenols / Q000737:chemistry; D009943:Organophosphorus Compounds / Q000737:chemistry; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D013379:Substrate Specificity; D015032:Zinc / Q000378:metabolism*
D007295:Inositol Phosphates; D009596:Nitrophenols; D009943:Organophosphorus Compounds; C002647:inositol 1-phosphate; C008644:nitrophenylphosphate; D000135:Acid Phosphatase; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase; D008274:Magnesium; D015032:Zinc