title: Identification of an insulin fragment produced by an insulin degrading enzyme, neutral thiopeptidase.
abstract: Previous studies have shown that neutral thiopeptidase (E.C.3.4.22.11, insulinase) degrades (processes) insulin with a high affinity (Km = 30 X 10(-9) M). In the current studies, insulin was subjected to digestion with a highly purified rat liver neutral thiopeptidase and the peptides generated were separated by HPLC using a C8 column. With the use of structural analysis (which included the determination of amino terminal residues and amino acid composition), the major product was identified as a peptide containing portions of both chains of insulin, A1 to A13 and B1 to B9 having two disulfide bonds, an interchain disulfide bond and presumably the intra-A chain disulfide bond as well. Examination of insulin-like biological activity using a primary cultured hepatocyte test system showed that the fragment promoted neither short-term (alpha-aminoisobutyric acid uptake) nor long-term (glycogen synthesis) bioactivities of insulin.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002478:Cells, Cultured; D055598:Chemical Phenomena; D002621:Chemistry; D003619:Dansyl Compounds; D006868:Hydrolysis; D007328:Insulin / Q000494:pharmacology; D007339:Insulysin; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008112:Liver Glycogen / Q000096:biosynthesis; D008297:Male; D010446:Peptide Fragments / Q000032:analysis / Q000494:pharmacology; D010447:Peptide Hydrolases; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000596:Amino Acids; D003619:Dansyl Compounds; D007328:Insulin; D008112:Liver Glycogen; D010446:Peptide Fragments; D010447:Peptide Hydrolases; D007339:Insulysin