Trypsin inhibitor from cow colostrum. Isolation, electrophoretic characterization and immunologic properties.

Trypsin inhibitor from cow colostrum has been purified by affinity chromatography of colostral proteins on insolubilized trypsin. The method described compares favourably, in both simplicity and yield, with previous methods developed for the isolation of this inhibitor. Gel electrophoresis followed by characterization of antitrypsin activity allows the demonstration of four molecular forms of bovine colostral trypsin inhibitor in both crude colostral whey and purified preparations of the inhibitor. Immunoelectrophoresis of each of these materials with antisera specific for this inhibitor reveals a single precipitation line of broad anodic mobility. By immunodiffusion tests, the precipitation lines in preparations of purified inhibitor and colostral whey appear immunologically identical. In contrast, absence of crossed reactivity was observed between bovine colostral trypsin inhibitor and trypsin inhibitors of bovine serum. This strongly suggests the high specificity of this inhibitor as a colostral and milk constituent.