STUDY OF HUMAN URINARY TRYPSIN INHIBITOR

III. Investigation of Plasma Protein with Reacts which an Antiserum Against Urinary Trypsin Inhibitor

Abstract

A plasma protein which forms a precipitation line with antiserum against urinary trypsin inhibitor was purified by ammonium sulfate fractionation, anti-urinary trypsin inhibitor rabbit IgG antibody coupled sepharose immunoadsorbent column chromatography and polyacrylamide gel disc electrophoresis. This purified protein was revealed homogenous by sodium dodecyl sulfate-polyacrylamide gel disc electrophoresis and had an apparent molecular weight of 90, 000. Immunoelectrophoresis of this protein also showed its homogeneity and the electrophoretic movility was the same as that of α-globulin.
Although this protein strongly inhibited trypsin activity and weakly chymotrypsin activity like urinary trypsin inhibitor and inter-α-trypsin inhibitor, it was immunologically distinct from inter-α-trypsin inhibitor.
These results suggest the possibility that purified protein may be a new proteinase inhibitor and the precursor of urinary trypsin inhibitor. There is another possibility that this purified protein is a cleavage product of inter-α-trypsin inhibitor and its antigenicity may be different from that of inter-α-trypsin inhibitor.