Activities of digestive enzymes of polar and subtropical echinoderms

Activities and characteristics of digestive enzymes of polar and subtropical echinoderms are similar. Specific adaptations to facilitate digestion at low temperature were not observed. Levels of chymotrypsin and β-glucosidase of digestive tissues of the Antarctic asteroids Odontaster validus and Odontaster meridionalis, and the Antarctic echinoid Sterechinus neumayeri, are comparable to levels of the asteroids Henricia downii and Astropecten articulatus from the Gulf of Mexico. α-Glucosidase activities are similar for S. neumayeri and A. articulatus. The pH of maximal activity is 7.5 for disaccharidases and 8.5–9.5 for chymotrypsin for both polar and subtropical species. Affinities for substrates were higher at 25°C than at 0°C for disaccharidases of all species. However, K_m values for chymotrypsin increased from 0 to 25°C. Lack of sufficient adaptation by polar echinoderms to facilitate digestion at low temperature may reduce their capacity to digest food.