Purification and characterization of an alpha-mannosidase of sea-squirt

An alpha-mannosidase was isolated from the extract of acetone powder of CHCl3-treated internal organs of the sea-squirt, Styela plicata. The enzyme was purified 4,110-fold in 11% yield. The preparation was fairly homogeneous on disc and SDS-polyacrylamide gel electrophoreses and Sephadex G-200 chromatography. The enzyme had an estimated molecular weight of 275,000 by gel chromatography and 70,000 by SDS-polyacrylamide gel electrophoresis, and was therefore considered to be a tetramer. The optimum pH for the enzyme activity was 3.4 but the stable pH range was from 4 to 6. The isoelectric point was 5.0. The enzyme was activated by Zn2+ but inhibited by Cu2+, Fe2+, Hg2+, and EDTA. The isolated enzyme released mannose not only from stem bromelin glycopeptide and ovalbumin glycopeptide but also from yeast mannan.