A comparative study of the digestive enzymes in the hepatopancreas of Jonah crab ( Cancer borealis) and rock crab ( Cancer irroratus)

Abstract

1. 1. In general, specific activities of enzymes were greater in the hepatopancreas of Cancer irroratus than in Cancer borealis. Optimum pH activity of each enzyme was similar for both species. 2. 2. Two proteinases similar in optimum pH (3·8 and 8·0) to those in gastric juice of Homarus americanus were found. Molecular weights were estimated at 16,700 and 20,500 for C. borealis and C. irroratus respectively. 3. 3. Among the carbohydrases, chitobiase was most predominant with a specific activity of 0·4 U/mg protein in lyophylised powder extract of C. irroratus. An unusually high level of β-galactosidase was found compared to other forms of Crustacea. There was also a considerable difference in molecular weights of α-glucosidase between C. borealis (47,000) and C. irroratus (86,000). 4. 4. In contrast to the American lobster, the hepatopancreas is the apparent source of production of certain esterases in C. irroratus and C. borealis.