1. Although only one activation peptide of bovine cationic trypsinogen has been reported previously, the peptide fraction obtained from activation mixtures shows several bands on paper electrophoresis at pH 6.5. 2. The major band was the peptide previously described. The band second in intensity of staining with ninhydrin (10-20% of that of the main band, as judged by eye) had an electrophoretic mobility consistent with its being related to the main peptide. It appeared on activation both of bulk commercial samples of trypsinogen and, as the Appendix shows, of samples prepared from pancreases obtained at the local abattoir. 3. The second peptide proved to be Phe-Pro-Val-Asp-Asp-Asp-Asp-Lys, and we conclude that it is another activation peptide. We discuss briefly the genetic and phylogenetic implications of our findings.
