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.
The insulin-stimulated cyclic AMP phosphodiesterase binds to a single class of protein sites on the liver plasma membrane
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M D Houslay, R J Marchmont; The insulin-stimulated cyclic AMP phosphodiesterase binds to a single class of protein sites on the liver plasma membrane. Biochem J 15 September 1981; 198 (3): 703–706. doi: https://doi.org/10.1042/bj1980703
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