On the mechanism of enzyme action. LXXIII. Studies on trypsins from beef, sheep and pig pancreas

Abstract

Bovine, ovine, and porcine trypsins are quite similar in pH and temperature optima, Michaelis-Menten constants, and kinetics of esterolytic activity, i.e., in those properties directly associated with the active center of the enzyme. Moreover, each enzyme is found to be inhibited to the same extent by dilute beef serum. In addition to the striking differences from its bovine and ovine counterparts in general protein characteristics, such as stability in alkaline media and electrophoretic behavior, porcine trypsin is found to have a lower isoelectric point than the other two trypsins. Data obtained indicate that the variation is due to its lower content of amide groups. Comparison of the amino acid composition and specific rotation of the trypsins substantiates the viewpoint that porcine trypsin possesses a structure distinctly different from the structures of the bovine and ovine enzymes which are seen to resemble each other quite closely. © 1962.