Sur le trypsinogène et la trypsine de porc

Abstract

A chromatographic procedure on carboxymethyl cellulose at pH 5.0 is described for the simultaneous purification of porcine trypsinogen and one of the porcine chymotrypsinogens. The yield calculated from the first extract of the gland in dilute sulfuric acid is 45% with a 2–3 fold purification. 1 kg of fresh pancreas gives at least 2.8 g of pure product.The amino acid compositions of bovine and porcine trypsinogens reveal some similarities. The molecular weight of both proteins is of the same order. But, a series of sizable differences of composition suggest that large regions of the molecules have in fact quite different structures.The diisopropylphosphoryl derivative of the trypsin formed by autoactivation of porcine trypsinogen can be purified by chromatography on carboxymethyl cellulose at pH 5.0. When the same technique is applied to active trypsin, a highly active, but slightly autolyzed, product is obtained.Autoactivation of porcine and bovine trypsinogens proceeds at about the same rate to give about the same maximal specific activity. Calcium ions have the same effect. In both cases, the activation process involves the specific splitting of a Lys-Ileu bond belonging to the N-terminal sequence of the chain and having on its left 4 aspartic acid residues. However, this bond is the 8th of the sequence in the case of porcine trypsinogen. The peptide set free is the octapeptide Phe-Pro-Thr-(Asp)4-Lys. Thus, the apparently essential region having the same structure in both trypsinogens is very narrowly restricted. Beyond it, structural modifications reflecting deep changes in the genetical information can be noted.Porcine trypsinogen and porcine trypsin have the same C-terminal sequence: Thr-(Ileu,Glu(NH2))-Ala-Asp(NH2).This identity is the first direct proof that trypsinogen activation does not involve any covalent modification in the C-terminal region of the chain.