Purification and Properties of Acid Phosphatase I From the Cellular Slime Mold Polysphondylium pallidum

Abstract

A procedure for the purification of a phosphomonoesterase, designated as acid phosphatase I, from the cellular slime mold Polysphondylium pallidum is described. Ammonium sulfate fractionation, gel filtration, and anion-exchange chromatography are utilized in this purification method. The enzyme was judged to be homogeneous by gel filtration and by acylamide gel electrophoresis. The molecular weight of the enzyme was estimated by gel filtration and density gradient centrifugation to be 150 000 daltons. Acid phosphatase I was shown to be relatively heat stable, and it lost no activity when kept at 4 °C, pH 7.35, for over 30 days. The pH optimum was 3.5, but the enzyme was found to be more stable when kept near neutral hydrogen ion concentrations. P. pallidum acid phosphatase I was most effective using the natural substrates, fructose-1,6-pbosphate, β-glycerolphosphate, and 5′-mononucleotides. Various compounds including known phosphatase inhibitors were tested as to their effect on the activity of the enzyme. The slime-mold acid phosphatase appears in many ways to be a typical acid phosphomonoesterase.