Effect of bile salt on digestive enzymes of rat pancreatic juice

Abstract

The activation and stability of various rat pancreatic juice zymogens and enzymes in the presence of trypsin and bile salts have been studied. Using model substrates to avoid earlier findings of detergent effects of bile salts, it was shown that sodium taurocholate does not affect tryptic activation or stability of endogenous pancreatic juice trypsin, procarboxypeptidase A (EC 3.4.2.1), procarboxypeptidase B (EC 3.4.2.2.), or 1he activities of amylase (EC 3.2.1.1), ribonuclease (EC 2.7.7.16), and lipase (EC 3.1.1.3). In the presence of the bile salt, the rate of chymotrypsin (EC 3.4. 4.5) activation and subsequent inactivation appeared to proceed more rapidly than without bile salt, and this effect was duplicated by using crystalline chymotrypsin. The addition of crystalline trypsin to rat pancreatic juice caused a rapid inactivation of sterol ester hydrolase (EC 3.1.1.13), whereas prior addition of bile salt completely protected the enzyme for as long as 90 minutes. Thus, of all pancreatic juice enzymes studied, the protective effect of taurocholate for sterol ester hydrolase appears to be unique and specific, and provides additional indirect evidence for the cofactor role of specific bile salts for this enzyme.