title: Demonstration of insulin degradation by thiol-protein disulfide oxidoreductase (glutathione-insulin transhydrogenase) and proteinases of pancreatic islets.
abstract: Homogenate preparations of pancreatic islets have been found to degrade insulin by cleavage of the interchain disulfide bonds, followed by proteolysis of the resulting A and B chains. A proteolytic system of the pancreatic islets splitting not only 125I-labeled insulin A chain but also 125I-labeled glucagon at pH 7.0, was shown to be activated by glutathione and inhibited by EDTA. The results suggest that pancreatic islets contain both the thiol-protein disulfide oxidoreductase (glutathione : protein-disulfide oxidoreductase, EC 1.8.4.2) and the A and B chain-degrading enzyme(s). The effects of EDTA argue against the implication of cathepsins in insulin breakdown under the experimental conditions employed.
mesh_terms: D000681:Amylases / Q000378:metabolism; D000818:Animals; D005934:Glucagon / Q000378:metabolism; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D007515:Islets of Langerhans / Q000201:enzymology*; D007700:Kinetics; D003012:Microbial Collagenase; D010088:Oxidoreductases / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism*; D011490:Protein Disulfide Reductase (Glutathione) / Q000378:metabolism*; D051381:Rats
chemical_list: D007328:Insulin; D005934:Glucagon; D010088:Oxidoreductases; D011490:Protein Disulfide Reductase (Glutathione); D000681:Amylases; D010447:Peptide Hydrolases; D003012:Microbial Collagenase