Inhibition by insulin of glucagon-dependent phospholipid methyltransferase phosphorylation in rat hepatocytes.
Addition of insulin to isolated rat hepatocytes prelabeled with [32P]phosphate inhibited glucagon-dependent phospholipid methyltransferase phosphorylation and activation. Insulin alone had no effect on either the phosphorylation of the enzyme or on its activity. The effect of insulin on glucagon-dependent phospholipid methyltransferase phosphorylation was dose-dependent and occurred at physiological doses of the hormone (10(-11)-10(-10) M). Analysis of 32P-labeled peptides after digestion with trypsin revealed only one site of phosphorylation regulated by glucagon (10(-8) M) in isolated rat hepatocytes. This site, as analyzed by HPLC and thin-layer chromatography, coincided with that phosphorylated by the cAMP-dependent protein kinase using purified rat liver phospholipid methyltransferase.
D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D005934:Glucagon / Q000037:antagonists & inhibitors*; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism; D008780:Methyltransferases / Q000378:metabolism*; D050941:Phosphatidyl-N-Methylethanolamine N-Methyltransferase; D050918:Phosphatidylethanolamine N-Methyltransferase; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats
D007328:Insulin; D010750:Phosphoproteins; D005934:Glucagon; D008780:Methyltransferases; D050918:Phosphatidylethanolamine N-Methyltransferase; D050941:Phosphatidyl-N-Methylethanolamine N-Methyltransferase