The lipase and esterase activities of the pancreas and small intestine of the chick

Abstract

In chicks from 1 to 30 days of age the lipase activity of the pancreas remained fairly constant, but the esterase activity of the small intestine increased markedly from 1 to 10 days of age and then remained constant. Of the three sections of the small intestine examined, lipase activity was greatest in the upper small intestine, whereas esterase activity was greatest in the duodenum. Although lipase activity was almost entirely confined to the pancreas, and esterase activity to the small intestine, evidence is given that both enzymes are present in both tissues. The optimum pH for chick pancreatic lipase with triolein as substrate was 8.7, whereas that for intestinal esterase with Tween 20 as substrate was 8.3. The hydrolytic activity of the pancreas with increasing concentrations of methyl butyrate and triacetin increased markedly at the saturation concentration with the appearance of emulsified substrate. The hydrolytic activity of the small intestine with methyl butyrate and triacetin was high when both substrates were present in true solution only, and increased only slightly with the appearance of emulsified substrate. Of a number of emulsified triglycerides investigated the hydrolytic activity of the pancreatic and small-intestinal lipase was highest with tributyrin, but decreased with increasing chain length of the constituent fatty acid. Tristearin and triolein were hydrolysed more readily by the pancreatic lipase than were the corresponding monoglycerides. Cholesterol esters and lecithin were hydrolysed by the pancreas, but not by the small intestine of the chick.