Enzymes of phospholipid metabolism in rat pancreatic islets: subcellular distribution and the effect of glucose and calcium.
The effect of glucose and calcium on the activities of the phosphatidylinositol cycle enzymes, CDP-diglyceride inositol transferase, diacylglycerokinase, and lysophosphatidylcholine 2-acyltransferase in rat pancreatic islets was studied. Calcium inhibited the activity of CDP-diglyceride inositol transferase but had no effect on lysophosphatidylcholine 2-acyltransferase and diacylglycerokinase activities. Upon preincubation of islets in a concentration of glucose known to stimulate insulin release, the activity of lysophosphatidylcholine 2-acyltransferase, but not that of diacylglycerokinase or the CDP-diglyceride inositol transferase, was stimulated. Subcellular fractionation of pancreatic islets showed that secretory granule membranes were enriched in CDP-diglyceride inositol transferase, whereas lysophosphatidylcholine 2-acyltransferase activity was highest in the microsomal membranes. The activation of 2-acyltransferase by incubating islets in insulinotropic glucose, and the calcium sensitivity of CDP-diglyceride inositol transferase, suggest that these enzymes may have roles in regulation of insulin secretion.
D000217:Acyltransferases / Q000378:metabolism; D000818:Animals; D051607:CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase; D002118:Calcium / Q000494:pharmacology*; D019852:Diacylglycerol Kinase; D005947:Glucose / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology*; D008245:Lysophospholipase / Q000378:metabolism; D008565:Membrane Proteins; D009097:Multienzyme Complexes / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology; D017855:Transferases (Other Substituted Phosphate Groups)
D008565:Membrane Proteins; D009097:Multienzyme Complexes; D010743:Phospholipids; D000217:Acyltransferases; D010770:Phosphotransferases; D019852:Diacylglycerol Kinase; D017855:Transferases (Other Substituted Phosphate Groups); D051607:CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase; C496767:Cdipt protein, rat; D008245:Lysophospholipase; C021782:lysophospholipase-transacylase; D005947:Glucose; D002118:Calcium