On bovine and porcine anionic trypsinogens

Abstract

The proportions of the anionic trypsinogens in cattle and pig pancreas do not exceed 10% of those of the well known cationic forms. Their amino acid compositions differ markedly, suggesting a relatively low degree of homology between both classes. The anionic trypsinogen from pig pancreas yielded after activation by entero-kinase a single peptide with 8 residues which was identical to that detached during the activation of the cationic zymogen in the same species. By contrast, activated cattle anionic trypsinogen yielded, not only a major octapeptide (90%) but also an hexapeptide (10%). The kinetic parameters of the enterokinase-catalyzed activation of the anionic trypsinogens appear to be distinctly more favorable than for their cationic analogs. This may compensate their lower proportions in the duodenum.