title: Analysis of proinsulin conversion activated by prior glucose: evidence that glucose stimulates synthesis of the conversion enzyme.
abstract: We examined the mechanism by which prior glucose exposure accelerates conversion of proinsulin to insulin in pancreatic islets. Using actinomycin A, introduced at different times after a 3H-leucine pulse to block the intracellular transport of proinsulin, transport was found to be slightly accelerated after prolonged glucose. However, computer simulation of pulse-chase experiments showed that activation of conversion is mostly due to increased converting activity. Measurement of islet procathepsin B by immunoprecipitation indicated synthesis of this enzyme was stimulated about two fold after glucose. Pre-exposure with tunicamycin inhibited the acceleration of conversion, suggesting that the converting system requires glycosylation.
authors.affiliation: Metabolic Research Unit, University of California, San Francisco 94143.
authors.forename: S
authors.initials: S
authors.lastname: Nagamatsu
authors.forename: G M
authors.initials: GM
authors.lastname: Grodsky
mesh_terms: D000968:Antimycin A / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D003198:Computer Simulation; D003594:Cytoplasmic Granules / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D066298:In Vitro Techniques; D007328:Insulin / Q000096:biosynthesis*; D007515:Islets of Langerhans / Q000378:metabolism*; D011384:Proinsulin / Q000378:metabolism*; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D007328:Insulin; D014415:Tunicamycin; D000968:Antimycin A; D011384:Proinsulin; D005947:Glucose