THE DIGESTIVE SYSTEM OF THE HOLOTHURIAN, CUCUMARIA ELONGATA. II. DISTRIBUTION OF THE DIGESTIVE ENZYMES

¹ Dove Marine Laboratory, University of Newcastle Upon Tyne, England

1. Estimations of proteases, carbohydrases, and lipases have been made on extracts of the different gut regions of Cucumaria elongata.

2. An endopeptidase of a trypsin-like nature and several exopeptidases have been detected, all with maximum activity in the intestine. Cellulase and lactase have not been detected, yet maltase and invertase were found in all regions of the gut, and showed their maximum activity in the constriction and intestine I. Amylase was found only in the constriction and intestine I. A strong esterase and a weaker "esterase-lipase" have been detected with practically uniform distribution throughout the gut, yet it is doubtful whether a true lipase, hydrolyzing long-chain fatty acids (C₁₈ and upwards), is present.

3. The work of earlier authors dealing with digestive enzymes and the sites of enzyme production in holothurians has been summarized. Results of quantitative estimations of digestive enzymes in Cucumaria, coupled with the results of previous histological and histochemical studies, lead to the conclusion that digestive enzymes are secreted by cells bordering the gut lumen.