Purification and properties of a beta-mannosidase from shrimp ( Penaeus japonicus) hepatopancreas

Abstract

1. 1. A β-mannosidase was purified ca 720-fold to homogeneity from Penaeus japonicus, with a final spec. act. of 252 U/mg of protein. 2. 2. By using SDS-polyacrylamide gel electrophoresis, the monomers of shrimp β-mannosidase were discovered to have mol. wts of 31,000 and those of human placental enzyme have similar mol. wts. 3. 3. The shrimp β-mannosidase has an isoelectric point (pI) of 5.6 ± 0.1, and the human placental enzyme has an identical pI. Both enzymes were sialyated. 4. 4. The shrimp β-mannosidase has a pH optimum at 5.0 and its K m was 123 μM with 4-methylumbelliferyl-β- d-mannopyranoside as substrate. The human enzyme has pH optimum at 4.5 and its K m was 10 μM. 5. 5. In contrast to the discovery of thermostability with human placental β-mannosidase, the shrimp enzyme was found to be labile to heating at 45°C for 20 min. Both enzyme activities were inhibited by Hg 2+ and Cd 2+ ions. However, the shrimp enzyme is significantly more sensitive to the inhibition.