Purification of α-Mannosidase from Hog Kidney and Its Action on Glycopeptides*

Abstract

1. α-Mannosidase (EC 3.2.1.24) was purified from hog kidney 1, 200 fold over the crude extract. The purified preparation had a specific activity of 19 units per mg protein when assayed at pH 4.6, the optimum pH, using p-nitrophenyl-α-D-mannoside as substrate, and was free from other glycosidases found in the kidney extract. The enzyme activity of crude preparations was heat stable, resisting a treatment at 60°C for 15 min, but the purified enzyme required Zn²⁺ to retain the activity even at room temperature. The enzyme solution could be stored indefinitely at —20°C without any loss of activity. 2. The purified enzyme was used to study the carbohydrate structures of glycopeptides from ovalbumin, Taka-amylase (EC 3.2.1.1) and stem bromelain (EC 3.4.4.24). From determinations of the liberated mannose and analysis of the remaining glycopeptides, aglycon specificity of the enzyme was discussed.