Purification and properties of multiple forms of mouse trypsinogen

Three trypsinogens and one chymotrypsinogen were found in and purified from the pancreas of a mouse strain (CFO). The molecular weights of the trypsinogens and the chymotrypsinogen were all estimated as 25 000. The enzyme properties of the three trypsinogens were studied and they showed very low Km values (3.2-6.5 microM) for the substrates, Bz-Arg-OEt and Tos-Arg-OMe, and the same pH optimum profile between pH 8.0-10.0. However, the ratios of catalytic rate constants, kcat (s-1), with Bz-Arg-OEt as substrates compared to that with Tos-Arg-OMe were very different. The values of Try-III were similar with the two substrates, Try-I was slightly higher value with Tos-Arg-OMe than with Bz-Arg-OEt, and the values of Try-II were much higher with Tos-Arg-OMe than with Bz-Arg-OEt. Also, the trypsinogens and the chymotrypsinogen were purified from pancreas of Mol-A strain mice. When the enzyme properties of the three trypsinogens were examined, one form of trypsinogen (Try-I) was shown to have different properties in kcat (s-1) for the two substrates, compared to the trypsinogen of CFO mice.