Human Pancreatic Proteolytic Enzymes and Protein Inhibitors

The purification of human proteolytic enzymes, i.e. two trypsins, two chymotrypsins and at least one elastase from activated extracts of human pancreas has been accomplished by a combination of affinity chromatography and conventional ion‐exchange chromatography on SE‐Sephadex. The enzymes thus obtained were homogeneous by several criteria: gel electrophoresis, equilibrium sedimentation and immunological assay. The molecular weight and amino‐acid composition of each preparation was determined and compared with those of other mammalian enzymes. The two trypsins showed only partial immunological identity while the two chymotrypsins were identical immunologically. The data raises the question of the number of the zymogens present in the human pancreas. In addition to the proteolytic enzymes, four protein inhibitors of proteolytic enzymes were also isolated from human pancreas. The procedure consisted of several steps that included gel filtration, affinity chromatography and isoelectric focusing. The two major components which accounted for most of the trypsin inhibitory activity were characterized and were apparently of the Kazal type. The more basic human pancreatic inhibitor had a pI of 8.7 and contained 48 amino acids with a molecular weight of 5200. The more acidic inhibitor had a pI of 6.5 and contained 39 amino acids with a molecular weight of 4300. Both inhibitors were capable of inhibiting bovine and two human trypsins. They did not inhibit two human chymotrypsins but had a weak capacity to inhibit bovine chymotrypsin.