Isolation and characterization of the cyanogen bromide peptides of 2 forms of porcine pancreatic amylase

Terminal residues of hog pancreatic amylase

Studies on the identification of the terminal residues in protease-free hog pancreatic alpha-amylase, prepared by glycogen precipitation, demonstrated the absence of free amino terminals when four different chemical procedures were used. These methods were based on reaction with fluorodinitrobenzene, trinitrobenzenesulfonic acid, dansyl chloride, and cyanate. In the search for the presence of a possible alpha-N-blocking group, an acetyl group was detected as acetic acid dinitrophenyl hydrazide after hydrazinolysis and dinitrophenylation. Quantitation of acetyl groups by a gas chromatographic or a specific enzymatic method yielded 0.7 mol of acetyl group per 51,000 g of protein. Other acyl groups, such as formyl or propionyl, were not found. Leucine was shown to be the carboxyl terminal residue by hydrazinolysis or by carboxypeptidase A digestion of acid denatured amylase. With either procedure, 0.8 mol of carboxyl terminal leucine was found per 51,000 g of protein. These findings are consistent with the proposal that hog pancreatic alpha-amylase is composed of a single, alpha-N-acetylated chain of molecular weight 50,000. Claims of other investigators for subunit and multichain structures for this enzyme are discussed in view of these end group data.

Biochemical genetics of alpha-amylase isozymes of the chicken pancreas

In the chicken population at large, three electrophoretically distinct pancreatic alpha-amylase isozymes were discovered. The isozymes were designated Pa 1, Pa 2, and Pa 3. The local population of chickens, however, possessed only isozymes Pa 2 and Pa 3 present as three phenotypes: Amy-2 B, consisting of isozyme Pa2; Amy2 BC, consisting of isozymes Pa 2 plus Pa 3; and Amy2 C, consisting of isozyme Pa 3. Pancreatic biopsy permitted the establishment of a breeding flock with defined amylase phenotypes. Matings of this flock established that amylases are inherited as codominant alleles at a single genetic locus. Further, there was no evidence of ontogenetic modification of the amylase isozymes. It was observed that amylase isozymes Pa 2 and Pa 3 each generated a family of at least three faster-migrating amylolytic proteins. These post-translationally modified amylases were designated Pa Xa, Pa Xb, and Pa Xc, where X represents the number of the progenitor amylase. Structural analyses of purified amylases demonstrated that all amylase isozymes are nonglycosidated, monomeric molecules of molecular weight 55,000. In addition, the data are consistent with the hypothesis that the faster-migrating amylases are produced by deamidation of asparagine and/or glutamine residues.