Binding of Pancreatic Proteolytic Enzymes

In human serum there are two protein fractions that are potent inhibitors to trypsin. These inhibitors travel with the a1-globulin and a2-globulin fractions when serum proteins are separated by electrophoresis (1-3). One ml of normal serum has sufficient amounts of trypsin inhibitor to neutralize the proteolytic effect of 1.15 (± 0.10) mg of crystalline trypsin. Approximately 90 per cent of the trypsin inhibitory proteins in serum migrate in the electrophoretic cell with the a1-globulin fraction, and the remainder with the a_2-globulin fraction (3). It is known that in many diseases of unrelated etiology the level of total serum trypsin inhibitor may be increased. This increase, therefore, is not specific for any disease, including acute pancreatitis. Also, it is likely that an increase in the a1globulin trypsin inhibitor is no more specific in the various diseases than is a sedimentation rate. However, the results of a previous study indicate that in acute pancreatitis the a2-globulin inhibitor decreases, and in severe pancreatitis it frequently disappears. The divergent changes of the two serum globulin trypsin inhibitors in acute pancreatitis result in a marked increase in the ratio of the a,to a2-globulin trypsin inhibitors. The decrease in the a2-globulin trypsin inhibitor in acute pancreatitis has been helpful in our laboratory in the diagnosis of acute pancreatitis (3). The determination of the serum a1,and a2-globulin trypsin inhibitors involves the lengthy procedure of serum protein separation by electrophoresis, elution of protein fractions which involves many hours, and then the determination of the trypsin-inhibiting capacity of the protein fractions. The present complexities of this procedure make the determination difficult for the routine hospital laboratory. Because of these factors we