Biomedical subjects

P St-Jean

Publications and source records attributed to P St-Jean.

21 records · Page 2Linked to original sources

PubMed1982

Isolation of zymogen granules from rat pancreas and characterization of their membrane proteins.

A zymogen granule fraction has been isolated from rat pancreas, and its purity has been assessed by biochemical and morphological criteria. Specific activities of two marker enzymes, amylase and chymotrypsin, are increased by 4.6 and 5.4-fold, respectively, as compared to the homogenate. The purified fraction is devoid of detectable RNA, DNA and 5'-nucleotidase, glucose-6-phosphatase, and cytochrome c oxidase activities. Electron micrographs confirm the absence of mitochondria, lysosomes, and rough endoplasmic reticulum fragments. Zymogen granule membranes were isolated from this fraction on a sucrose gradient following lysis in alkaline buffer. Secretory contaminants were efficiently removed from the membranes as indicated by experiments in which labeled secretory proteins were added during the isolation procedure and secondly by measuring residual levels of amylase and chymotrypsin. Three enzyme activities were found in the membranes: thiamine pyrophosphatase, ATP-diphosphohydrolase, and low levels of acid phosphatase. Membrane proteins were solubilized by urea-Triton X-100 and separated in double-dimension (isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis). Isoelectric point and molecular weight of each protein band were determined.

Animals↗

PubMed1981

Distribution of amylase and chymotrypsin in four regions of the rat pancreas.

Recent observations have confirmed the existence of more than one pool of secretory proteins in the rat pancreatic tissue. To determine if these different pools could be located in the different regions of the rat pancreas, the amylase and chymotrypsin contents have been measured in the biliary, duodenal, gastric, and splenic regions. On a tissue DNA content, protein content, or a fresh weight basis, the proportions of these two enzymes are comparable in the four regions. It is therefore postulated that heterogeneity of enzyme composition exists either within these regions or within the acinar cell itself.

Amylases↗

PubMed1980

Characterization and purification of a calcium-sensitive ATP diphosphohydrolase from pig pancreas.

An ATP diphosphohydrolase (EC 3.6.1.5) from the pancreas of the pig has been characterized and purified. The enzyme which has an optimum pH between 8 and 9 is specific for diphospho- and triphosphonucleosides. The Km values for ADP and ATP are 7.4 and 7.3 x 10(-4) M, respectively, and the purified enzyme has specific activities of 13 and 15.2 mumol of Pi/min/m of protein, respectively. It requires calcium or magnesium ions and it is insensitive to ATPase inhibitors, namely oligomycin, ouabain, and ruthenium red, and to levamisole, an inhibitor of alkaline phosphatase. Denaturation experiments, by heat and trypsin treatments, indicated that only one enzyme is involved. This is confirmed by the solubilization and purification process and by polyacrylamide gel electrophoresis. A 270-fold purification was obtained by centrifugation and successive column chromatography on Sepharose 4B and Affi-Gel blue. It is a glycoprotein with a molecular weight of 65,000 as estimated by polyacrylamide gel electrophoresis.

Animals↗