Purification and characterization of pepsinogens and a unique pepsin from rat stomach

Four pepsinogens (1, 2, 3 and 4) (zymogens of pepsin A, EC 3.4.23.1, or pepsin C, EC 3.4.23.3) were purified from the fundic mucosa of rat stomach to homogeneous states as judged by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and a unique pepsin was purified from pepsinogen 1. The molecular weights of pepsinogens 1, 2, 3 and 4 were 42 000, 40 000, 40 500 and 39 000, respectively, and those of the respective activated pepsins (1, 2, 3 and 4) were 35 500, 40 000, 35 500 and 37 000, respectively, as estimated by polyacrylamide gel electrophoresis. The amino acid compositions of these four zymogens differed, but resembled those of pepsinogen Cs from various animal species. Rabbit antiserum prepared against pepsinogen 1 reacted with pepsinogen 2, but not with pepsinogens 3 or 4. The precipitin line against pepsinogen 1 fused completely with that against pepsinogen 2. Purified pepsin 1 was a unique pepsin showing remarkable stability in alkali. It resembled pepsin A with respect to inhibition by pepstatin and pepsin C with respect to its amino acid composition, but had properties intermediate between those of pepsin A and C with respect to its optimal pH (2.1 to 3.1) with hemoglobin and activity on N-acetyl-L-phenylalanyl-L-diiodotyrosine.