PURIFICATION AND SOME PROPERTIES OF A MG2-ACTIVATED ACID-PHOSPHATASE FROM RAT TESTIS()

1. The acid phosphatase (AcPase, EC 3.1.3.2) IV from rat testicular ti ssue was purified to apparent homogeneity. 2. The enzyme displays a na tive molecular weight of 70 kDa determined on gel permeation chromatog raphy on a Sephadex G-100 column and 68 kDa using linear 5-20% sucrose density gradient centrifugation. The subunit molecular weight on SDS- PAGE analysis is 67 kDa, suggesting that the enzyme is a monomeric pro tein.3. The enzyme does not bind to Concanavaline A-Sepharose 4B colum n, indicating that it is not a glycoprotein. 4. The rat testis AcPase IV is a metal activated enzyme in which Mg2+ is the metal activating a gent with a K-a = 0.88 x 10(-3) M. The Michaelis constant for p-nitrop henylphosphate, in the presence of saturating concentrations of Mg2+ i ons, is 0.23 x 10(-3) M. 5. The enzyme preferentially hydrolizes p-nit rophenylphosphate, phenylphosphate and ATP.