title: Ca2+-dependent cyclic nucleotide phosphodiesterase is activated by poly(L-aspartic acid).
abstract: Ca2+-dependent cyclic nucleotide phosphodiesterase (Ca2+-PDE) activity was stimulated by poly(L-aspartic acid) but not by poly(L-glutamic acid), poly(L-arginine), poly(L-lysine), and poly(L-proline). This activation was Ca2+ independent and did not further enhance the activation of Ca2+-PDE by Ca2+-calmodulin (CaM). Poly(L-aspartic acid) produced an increase in the Vmax of the phosphodiesterase, associated with a decrease in the apparent Km for the substrate, such being similar to results obtained with Ca2+-CaM. Poly(L-aspartic acid) did not significantly stimulate myosin light chain kinase and other types of cyclic nucleotide phosphodiesterase. CaM antagonists such as N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), trifluoperazine, and chlorpromazine selectively antagonized activation of the enzyme by poly(L-aspartic acid). Kinetic analysis of W-7-induced inhibition of activation of phosphodiesterase by poly(L-aspartic acid) was in a competitive fashion, and the Ki value was 0.19 mM. On the other hand, prenylamine, another type of calmodulin antagonist that binds to CaM at sites different from the W-7 binding sites, did not inhibit the poly(L-aspartic acid)-induced activation of Ca2+-dependent cyclic nucleotide phosphodiesterase. These results imply that poly(L-aspartic acid) is a calcium-independent activator of Ca2+-dependent phosphodiesterase and that aspartic acids in the CaM molecule may play an important role in the activation of Ca2+-PDE.
mesh_terms: D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000097:blood* / Q000302:isolation & purification; D001792:Blood Platelets / Q000201:enzymology; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000097:blood* / Q000302:isolation & purification / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D007700:Kinetics; D010455:Peptides / Q000494:pharmacology*; D013329:Structure-Activity Relationship
chemical_list: D002147:Calmodulin; D010455:Peptides; C017645:polyaspartate; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases; D002118:Calcium