title: Effects of zinc chloride on the hydrolysis of cyclic GMP and cyclic AMP by the activator-dependent cyclic nucleotide phosphodiesterase from bovine heart.
abstract: In the presence of 10 micrometer Ca2+ and 5 mM Mg2+ (or 0.25 mM Mg2+), the addition of 100 micrometer Zn2+, Ni2+, Co2+, Fe2+, Cu2+ or 1 mM Mn2+ resulted in varying degrees of stimulation or inhibition of 10(-6) M cyclic GMP and cyclic AMP hydrolysis by the activator-dependent cyclic nucleotide phosphodiesterase from bovine heart in the absence or presence of phosphodiesterase activator. The substrate specificity of the enzyme was altered under several conditions. The addition of Zn2+ in the presence of 5 mM Mg2+ and the absence of activator resulted in the stimulation of cyclic GMP hydrolysis over a narrow substrate range while reducing the V 65% due to a shift in the kinetics from non-linear with Mg2+ alone to linear in the presence of Zn2+ and Mg2+. Zn2+ inhibited the hydrolysis of cyclic GMP and cyclic AMP in the presence of activator with Ki values of 70 and 100 micrometer, respectively. Zn2+ inhibition was non-competitive with substrate, activator and Ca2+ but was competitive with Mg2+. In the presence of 10 micrometer Ca2+ and activator, a Ki of 15 micrometer for Zn2+ vs. Mg2+ was noted in the hydrolysis of 10(-6) M cyclic GMP. Several effects of Zn2+ are discussed which have been noted in other studies and might be due in part to changes in cyclic nucleotide levels following phosphodiesterase inhibition.
mesh_terms: D000818:Animals; D002413:Cations, Divalent; D002417:Cattle; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D015032:Zinc / Q000494:pharmacology*
chemical_list: D002413:Cations, Divalent; D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases; D006152:Cyclic GMP; D015032:Zinc