Purification and Characterization of Canine Pepsinogen

Pepsinogen has been purified from the fundic mucosa of the dog. The preparation is homogeneous by chromatography, amino terminal analysis, ultracentrifugation, electrophoresis on cellulose acetate strips, and disc electrophoresis. Analysis indicates the presence of 352 amino acid residues, at least 12 moles of carbohydrate including some amino sugars, and 1 mole of organic phosphate per mole of protein. The amino terminus is Ala-Ile-. Canine, porcine, and bovine pepsinogens are similar in size, in the large number of acidic and small number of basic residues, and in the number of aromatic residues and cystine. The main differences are in the number of hydroxy amino acids and methionines; canine pepsinogen with 8 methionine residues is unlike the other mammalian zymogens, but resembles dogfish and chicken pepsinogens. The molecular weight of canine pepsinogen is 39,900 by amino acid and carbohydrate content and 41,667 by ultracentrifugation; the sedimentation coefficient, s20,ω, is 3.38 S and the diffusion coefficient, D20,ω, is 7.37 x 10-7 cm2 per sec