Purification and characterization of porcine pepsinogen B and pepsin B.
Porcine pepsinogen B was prepared from extracts of adult porcine fundic mucosa. Immunoelectrophoresis showed no immunochemical cross-reactions between pepsinogen B and other porcine gastric zymogens. Pepsin B was purified after activation of the zymogen. The enzyme showed an optimum of general proteolytic activity at pH 3.0. Activation of pepsinogen B at pH 2 resulted in formation of the covalent intermediate (pseudo-pepsin B) by proteolytic cleavage of bond Met16p-Glu17p (pig pepsinogen A numbering, "p" indicates residues of the prosegment peptide). Pseudopepsin B was stable at pH 2. The intermediate was converted to pepsin B at pH 5.5. The overall activation of pepsinogen B was much slower than found for other investigated gastric zymogens. During the conversion of pepsinogen B to mature pepsin B a segment of 43 amino acid residues was cleaved from the N-terminal of pepsinogen B. The amino acid sequence of the prosegment and the first 24 residues of pepsin B was determined. Relative to porcine pepsinogen A, progastricsin, and prochymosin, the following degrees of identities were observed: 40, 55, and 51%.
Nielsen
P K
PK
Department of Protein Chemistry, University of Copenhagen, Denmark.
Foltmann
B
B
D000595:Amino Acid Sequence; D000818:Animals; D005748:Gastric Fundus / Q000201:enzymology; D005753:Gastric Mucosa / Q000201:enzymology; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010434:Pepsin A / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D010435:Pepsinogens / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D013270:Stomach / Q000201:enzymology*; D013552:Swine
D007527:Isoenzymes; D010435:Pepsinogens; D010434:Pepsin A; C095924:pepsin B