Müller K, Zwilling R
Hoppe Seylers Z Physiol Chem. 1975 Jul;356(7):1173-5.
The study of six trypsins (crayfish, dogfish, horse, pig, sheep, bovine) showed that among these the highest lysine + arginine content and the highest inactivation rate occur in specialized herbivorous animals with extreme length of gut. Since the autocatalytic degradation in trypsins can take place only at lysine or arginine residues, an accumulation of basic amino acids, the increase of the autocatalytic inactivation rate and the relative length of gut might be correlated during the evolution of mammalian trypsins.