Isolation of urinary trypsin inhibitor-like inhibitor from human lung cancer tissue.

In the present study, a trypsin inhibitor was first extracted from lung cancer tissue and purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A final yield of 20 to 60 micrograms of inhibitor with a specific activity of 2040 units/mg of protein was obtained from 1 g of original lung cancer tissue. This inhibitor inhibited trypsin strongly, plasma kallikrein weakly, and plasmin more weakly, and its molecular weight was approximately 43,000 to 45,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its antigenicity was confirmed to be quite the same as that of human urinary trypsin inhibitor by double immunodiffusion, immunoelectrophoresis, and neutralization with anti-urinary trypsin inhibitor rabbit immunoglobulin.