The catalytic subunit of protein kinase A triggers activation of the type V cyclic GMP-specific phosphodiesterase from guinea-pig lung.
The type V cyclic GMP phosphodiesterase was partially purified from the high-speed supernatant of guinea-pig lung. The isoenzyme displayed linear kinetics for cyclic GMP hydrolysis, with Km = 2.2 +/- 0.2 microM and Vmax. = 1.2 +/- 0.08 nmol/min per mg. The selective type V phosphodiesterase inhibitor Zaprinast inhibited cyclic GMP hydrolysis with IC50 (concn. giving 50% inhibition) = 0.45 +/- 0.08 microM. Isobutylmethylxanthine promoted a 3-fold increase in the binding of cyclic GMP to the isoenzyme. The addition of the catalytic subunit of protein kinase A to an activation cocktail containing the partially purified type V phosphodiesterase resulted in a marked increase in Vmax. for cyclic GMP hydrolysis (approximately 10-fold at 40 units of protein kinase A). We have suggested that protein kinase A triggers phosphorylation of the phosphodiesterase, which results in activation of phosphodiesterase activity. In addition, the sensitivity to inhibition by Zaprinast is severely decreased (the IC50 for inhibition is 7.5 +/- 1.1 microM), suggesting that the potency of phosphodiesterase inhibitors is effected by phosphorylation of the enzyme.
Burns
F
F
Department of Physiology and Pharmacology, University of Strathclyde, Royal College, Glasgow, Scotland, U.K.
Rodger
I W
IW
Pyne
N J
NJ
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors; D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D006168:Guinea Pigs; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008168:Lung / Q000201:enzymology*; D046911:Macromolecular Substances; D011494:Protein Kinases / Q000378:metabolism*; D011688:Purinones / Q000494:pharmacology; D013379:Substrate Specificity
D007527:Isoenzymes; D046911:Macromolecular Substances; D011688:Purinones; D011494:Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; C011145:zaprinast