Allosteric regulation of phosphodiesterase from Portulaca callus by cGMP and papaverin |
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Authors: | Rudolf Endress |
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Affiliation: | Lehrstuhl für Botanische Entwicklungsphysiologie der Universität, 7000 Stuttgart-Hohenheim, Emil-Wolffstr. 25, Germany |
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Abstract: | Three fractions of phosphodiesterase activity capable of hydrolysing cyclic 3′,5′-AMP and cyclic 3′,5′-GMP were purified from Portulaca callus. Hydrolysing bis-(p-nitrophenyl)-phosphate, two fractions showed linear Lineweaver-Burk plots. One fraction showed positive cooperativity. This fraction can be activated competitively by blue dextran, indicating a possible allosteric regulation by nucleotides, demonstrated by changing from being positively cooperative, to following Michaelis-Menten kinetics by cGMP and papaverin. cGMP triggers an enzyme highly active against 3′,5′cAMP and 3′5′cGMP, and papaverin triggers high activity against 2′,3′cAMP, demonstrated by two separate enzyme fractions. |
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Keywords: | Portulacaceae phosphodiesterase allosteric interconversion papaverin cAMP cGMP. |
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