title: Divalent metal cation requirement and possible classification of cGMP-inhibited phosphodiesterase as a metallohydrolase.
abstract: cGMP-inhibited phosphodiesterase (cGI-PDE) has been found to require a divalent metal cation for cAMP hydrolysis. The cGI-PDE isolated from human platelets exhibited significantly higher enzymatic activity when incubated with Mn2+, Mg2+, and Co2+. The addition of Zn2+, Cd2+, Ca2+, K+, or Na+ to the enzyme did not enhance the activity and, when present in high concentration (> 1.0 microM), Zn2+ and Cd2+ inhibited the enzymatic activity of cGI-PDE. The inhibition by Zn2+ (and Cd2+) was partially prevented by preincubation of the enzyme with Mn2+. The enzyme was also inhibited by metal chelators EDTA and 1,10-phenanthroline and not by their non-metal-chelating analogs. The partial protection against chelation (and inhibition) was afforded by AMP (the product of cAMP hydrolysis).
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000145:classification / Q000378:metabolism*; D001792:Blood Platelets / Q000201:enzymology*; D002413:Cations, Divalent / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D008666:Metalloendopeptidases / Q000145:classification*
chemical_list: D002413:Cations, Divalent; D000242:Cyclic AMP; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D008666:Metalloendopeptidases