Purification and some properties of lysosomal alpha-glucosidase of rat liver

Acid alpha-glucosidase was purified from the lysosomal/mitochondrial fraction of rat liver by acid precipitation, ammonium sulphate precipitation and affinity chromatography on Sephadex G 100, resulting in 17000-fold enrichment from that of the liver homogenate. The molecular weight of the enzyme was estimated to be 125000 from analytical gel filtration experiments. On SDS-polyacrylamide gel electrophoresis the purified enzyme showed only a single band having an apparent molecular weight of about 64000. Based on these results, it is concluded that lysosomal liver alpha-glucosidase consists of two subunits. The discontinuous system of SDS-polyacrylamide gel electrophoresis, however, revealed two closely migrating protein bands suggesting heterogeneity of the enzyme subunits.