Nuclear chemistry

Gene

Cyclic nucleotide

Phosphodiesterase

Chromatography

Calcium

Biochemistry

Organic chemistry

Nucleotide

Enzyme

Hydrolysis

Activator (genetics)

Chemistry

EGTA

Cyclic nucleotide phosphodiesterase

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics

Most (85% or more) of the cyclic nucleotide phosphodiesterase (3′:5′-cyclic-AMP 5′-nucleotidohydrolase, EC 3.1.4.17) activity of pig coronary arteries was found in the 40 000 × g supernatant fraction of homogenates of the intima plus media layer. Chromatography of the soluble fraction of this layer on DEAE-cellulose resolved two phosphodiesterase activities and a heat stable, non-dializable activator. Peak I activity had apparent Km values of 2–4 μM for cyclic GMP and 40–100 μM for cyclic AMP. Peak II activity was relatively specific for cyclic AMP and exhibited apparent negatively cooperative behavior. Peak I but not peak II activity could be stimulated 3–8-fold by the addition of the boiled activator fraction or a boiled crude supernatant fraction. Cyclic AMP hydrolysis by peak I or peak II was more rapid in the presence of Mn2+ than Mg2+, but the latter promoted hydrolysis of cyclic GMP by peak I more effectively than did Mn2+ in the presence of activator. In the absence of added metals, ethylene bis(oxyethylenenitrilo)tetra-acetic acid (EGTA) and EDTA both inhibited hydrolysis of cyclic AMP and cyclic GMP by phosphodiesterase activities in the supernatant fraction and in peak I, but EDTA produced more complete inhibition at lower concentrations than did EGTA. Imidazole (1 μM to 10 mM) had virtually no effect on the hydrolysis of cyclic AMP or cyclic GMP catalyzed by either of the two separated peaks or by total phosphodiesterase activities in crude supernatant or particulate fractions.

Cyclic nucleotide phosphodiesterase activities of pig coronary arteries