Purification and properties of α-d-mannosidase from the limpet, Patella vulgata

1. α-Mannosidase from the limpet, Patella vulgata, was purified nearly 150-fold, with 40% recovery. β-N-Acetylglucosaminidase was removed from the preparation by treatment with ethanol. The final product was virtually free from β-galactosidase. 2. Limpet α-mannosidase was assayed at pH3.5 and at this pH it was necessary to add Zn2+ for full activity. At pH5, the enzyme had the same activity in the presence or absence of added Zn2+. 3. On incubation at acid pH, the enzyme underwent reversible inactivation, which was prevented by adding Zn2+. 4. EDTA accelerated inactivation and the addition of Zn2+ at once restored activity. No other cation was found to reactivate the enzyme. 5. Cl- had an unspecific effect on hydrolysis by limpet α-mannosidase. It increased the rate of reaction with substrate. The anion did not prevent or reverse inactivation by EDTA. 6. It is concluded that α-mannosidase is a metalloenzyme or enzyme–metal ion complex, dissociable at the pH of activity, and that it requires Zn2+ specifically.