Purification of alpha-mannosidase activity from Indian lablab beans

Seeds of Dolichos lablab var. typicus (Indian lablab beans) contain a glucose/ mannose specific lectin that was affinity purified on Sepharose mannose columns in our laboratory. The unbound fraction from this matrix showed alpha-mannosidase activity. In the present study this has been purified to homogeneity by a combination of ion-exchange, hydrophobic chromatography and gel filtration. Purified alpha-mannosidase had an apparent molecular weight of 195,000 +/- 5,000 with 4.5% carbohydrate. On SDS-PAGE under reducing conditions, the enzyme dissociated into two major bands corresponding to Mr 66,000 and Mr 44,000. An antibody to the well studied jack bean alpha-mannosidase cross-reacts with the enzyme from the lablab beans suggesting antigenic similarity between these two legume mannosidases.