A sialidase from the hepatopancreas of the shrimp Penaeus japonicus (Crustacea: Decapoda): Reversible binding with the acidic beta-galactosidase

Abstract

1. The sialidase purified from the hepatopancreas of Penaeus japonicus is able to bind the acidic beta-galactosidase in vitro. No protective protein, M r 32,000, was detected in either purified enzyme preparation. 2. The specific activity of the isolated sialidase is 55.0 mU/mg of protein. After polyacrylamide gel electrophoresis under denaturing conditions, the purified shrimp enzyme was found to consist of monomers of M r 32,000. 3. The sialidase from shrimp has an isoelectric point (pI) of 4.6 ± 0.1. 4. The shrimp enzyme has the pH optimum at 5.0 and its K m was 5.5 μM with 2'-(4-methylumbelliferyl)-α- d- N-acetylneuraminic acid as substrate. The enzyme activity was inhibited by either Hg 2+ or Cu 2+ ions.