Abstract
Regulation of Ca 2+-dependent (peak I) and Ca 2+-independent (peak II) phosphodiesterases from the heart by various fatty acyl esters and phospholipids were studied. DL-Palmitoylcaritine stimulated the basal activity (in the absence of Ca 2+) of peak I enzyme, while non-competitively inhibiting peak II enzyme with respect to cyclic AMP. It had no effect on other species of Ca 2+-independent phosphodiesterases, including cyclic AMP- and cyclic GMP-specific enzymes from the lung, and cyclic CMP enzyme from the liver. Palmitoyl-CoA and phosphatidyl-serine also stimulated the basal activity of peak I enzyme, but they were without effect on peak II enzyme. In comparison, DL-palmitoylcarnitine inhibited Ca 2+-dependent activity of cardiac myosin light chain kinase, whereas phosphatidylserine was without effect. It is conceivable that differential regulation of phosphodiesterases by these lipids could profoundly alter the levels or effects, or both, of cyclic nucleotides and Ca 2+ in the myocardium.
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