Rat liver neutral alpha-glucosidase: isolation and characterization

Neutral alpha-glucosidase was isolated from rat liver by Sephadex G-150 gel filtration and polyacrylamide gel electrophoresis at pH 8.9. The enzyme was found to exist in two major forms: alpha-glucosidase AB and alpha-glucosidase C. The neutral alpha-glucosidase C was purified to apparent homogeneity and biochemically characterized. The enzyme form accounts for 25-30% of the total enzyme activity, has a pH optimum at 6.0-6.5 and is thermostable. The apparent Km values for alpha-glucosidase C with maltose, MUF-alpha-D-glucopyranoside and glycogen as substrates were 1.22 mM, 0.47 mM and 68.9 mg, respectively. The finding that glycogen can serve as substrate for neutral alpha-glucosidase C suggests its involvement in glycogen metabolism.