The Protein Composition of Human Pancreatic Juice

Human pancreatic juice contains amylase, lipase, ribonuclease, deoxyribonuclease, proelastase, procarboxypeptidase A, procarboxypeptidase B, chymotrypsinogen, and trypsinogen, as well as a trypsin inhibitor. The level of the inhibitor is such that 1 ml of pancreatic juice containing 4 mg of protein will inhibit about 0.08 mg of bovine trypsin. The inhibitor is a small, basic protein, soluble in 2.5% trichloracetic acid. It differs from the Kunitz bovine inhibitor in its slower migration rate in polyacrylamide gels at pH 4.1 and in its kinetic properties. 2. The proteins of human pancreatic juice have been separated into anionic and cationic fractions at pH 6.5. The cationic proteins include amylase, lipase, RNase, and pancreatic trypsin inhibitor; the anionic proteins include chymotrypsinogen, procarboxypeptidases A and B, and two components showing tryptic activity. 3. The cationic proteins have been separated on polyacrylamide gels and identified by histochemical methods. Zones containing amylase, lipase, RNase, and pancreatic trypsin inhibitor have been localized.