title: The insulin-stimulated cyclic AMP phosphodiesterase binds to a single class of protein sites on the liver plasma membrane.
abstract: The peripheral cycle AMP phosphodiesterase from rat liver plasma membranes binds with high affinity (2.4 nM) to a single class of receptor sites on the liver plasma membrane. These receptor sites appear to be proteins, as they are trypsin- and heat-labile. The sensitivity of these sites to denaturation by trypsin and heat is a first-order process. The presence of Ca2+ (5 mM) increases the affinity of these sites for the enzyme, but does not alter their total number. The receptor sites and the cyclic AMP phosphodiesterase occur in similar numbers, at around 2 pmol/mg of plasma-membrane protein. It is proposed that the peripheral, liver plasma-membrane cyclic AMP phosphodiesterase is attached to a specific site on the insulin receptor and that the binding of insulin to the receptor site triggers a conformational change in the enzyme such that the enzyme can be phosphorylated and activated by an endogenous cyclic AMP-dependent protein kinase.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D007328:Insulin; D008565:Membrane Proteins; D015105:3',5'-Cyclic-AMP Phosphodiesterases