Purification and chemical characterization of human acidic alpha-D-mannosidase

The acidic alpha-D-mannosidase (EC 3.2.1.24) has been purified from human placentae. Milligram quantities of the enzyme were obtained from several placentae, using a step-wise purification procedure which includes Con A-Sepharose treatment, acetone precipitation, heat treatment, DEAE-cellulose column chromatography and preparative disc electrophoresis. A high degree of purity of the purified enzyme was demonstrated by acrylamide gel electrophoresis, isoelectric focusing, and sedimentation equilibrium centrifugation. Immunological homogeneity of the preparation was demonstrated by a single precipitin line between the antiserum and purified, or partially purified enzyme preparation. The amino acid and carbohydrate composition of the enzyme was determined. The enzyme was found to be a glycoprotein containing 13.5% carbohydrate. The molecular weight of the enzyme was estimated at 205,000 +/- 18,400.