title: Guanine nucleotides and adenosine "R(i)'-site analogues stimulate the membrane-bound low-K(m) cyclic AMP phosphodiesterase of rat adipocytes.
abstract: Concentrations of GTP or Gpp(NH)p up to 300 nM activated the membrane-bound low-K(m) cyclic AMP phosphodiesterase of rat adipocytes, while higher concentrations of these nucleotides reversed this activation. The adenosine analog N6-phenylisopropyladenosine (N6-PIA) elicited a dose-dependent stimulation of this enzyme (K(act) = 3 nM), an effect which did not require GTP and which was additive with the GTP-induced stimulation. Both the N6-PIA and GTP stimulations were rapid, reversible and resulted from an increase in V(max). In contrast, neither GTP, nor N6-PIA affected the soluble low-K(m) cyclic AMP phosphodiesterase.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism*; D000241:Adenosine / Q000031:analogs & derivatives*; D000273:Adipose Tissue / Q000201:enzymology*; D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000201:enzymology; D004789:Enzyme Activation; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D010660:Phenylisopropyladenosine / Q000494:pharmacology*; D011485:Protein Binding; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D010660:Phenylisopropyladenosine; D006165:Guanylyl Imidodiphosphate; D006160:Guanosine Triphosphate; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D000241:Adenosine