title: Phospholipid modulation of low-Km cyclic AMP phosphodiesterase activity on rat adipocyte microsomes.
abstract: The ability of nine phospholipids to alter the activity of low-Km cyclic AMP phosphodiesterase was examined in microsomal fractions of rat adipocytes. The enzyme was activated by phosphatidylserine (21% at 300 microM) and phosphatidylglycerol (36% at 300 microM). The activation was concentration dependent over the range 1-1000 microM. Six other phospholipids were without effect. Phosphatidylinositol 4-phosphate inhibited the activity of the enzyme over the same range of concentrations (26% at 300 microM). Phosphatidylserine also activated a partially purified preparation of the enzyme, whereas phosphatidylinositol 4-phosphate was ineffective. The mechanism of the activation of the enzyme by phosphatidylserine and phosphatidylglycerol involved an increase in the apparent Vmax of the enzyme, while the inhibition by phosphatidylinositol 4-phosphate was associated with an increase in the Km of the enzyme for substrate. The phospholipid modulators of low-Km cyclic AMP phosphodiesterase activity did not alter the activity of high-Km cyclic AMP phosphodiesterase. The ability of phospholipids to alter the activity of low-Km cyclic AMP phosphodiesterase in native membranes suggests a possible role for phospholipids in metabolic regulation.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000273:Adipose Tissue / Q000201:enzymology*; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D010743:Phospholipids / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D010743:Phospholipids; D015105:3',5'-Cyclic-AMP Phosphodiesterases