STUDY OF HUMAN URINARY TRYPSIN INHIBITOR

I. Purification and Physicochemical Properties of Human Urinary Trypsin Inhibitor

Abstract

A procedure was presented for purifying a trypsin inhibitor in normal human urine. The purifying method was gentle and easy. The final product was homogenous as judged by disc gel electrophoresis, sodium dodecyl sulfate gel electrophoresis and immunoelectrophoresis. Its molecular weight was 67, 000 when estimated by sodium dodecyl sulfate gel electrophoresis and gel filtration with Sephadex G-100. It migrated in the prealbumin region in immunoelectrophoresis. It was confirmed that urinary trypsin inhibitor was purified as the same native form as in human urine.
The activity of this inhibitor was stable against acid (pH 2-4) and also heat (100°C, 30min) under acid condition. It inhibited strongly the activity of trypsin, and weakly those of kallikrein and chymotrypsin, but did not inhibit the activities of urokinase, plasmin or thrombin.
This inhibitor formed a single precipitin line with rabbit antiserum against this inhibitor, but did not react with rabbit antisera against α₁-antitrypsin, α₂-macroglobulin, inter-α-trypsin inhibitor, C1-inhibitor and human whole serum. On the other hand, the existence of a protein in serum reacting with anti-urinary trypsin inhibitor rabbit serum was reconfirmed and it migrated into the α-globulin region in immunoelectrophoresis. This protein in serum may be a different protease inhibitor from known trypsin inhibitors in human serum.