title: Ca2+/protein modulator-dependent and -independent cyclic GMP phosphodiesterase from hog heart.
abstract: Ca2+/protein modulator-dependent and -independent guanosine 3':5'-monophosphate (cGMP) phosphodiesterases were separated from hog heart. The protein modulator-free Ca2+/protein modulator-dependent enzyme was partially purified by repeated DEAE-cellulose column chromatography and heat treatment. The final preparation of this enzyme showed no significant basal activity under the standard assay conditions. Lineweaver-Burk plots of the Ca2+/protein modulator-dependent enzyme activity indicated the presence of only a single kinetic form of the enzyme with Km=2.0 X 10(-6) M for for cGMP, whereas the plots for the independent enzyme were anomalous, showing both high and low K m values for cGMP. The Ca2+/protein modulator-dependent enzyme proved relatively stable at 48 degrees C for 1 h, but the independent form lost its activity under the same conditions. Furthermore, 50% inhibition of the dependent enzyme activity, but only 10% inhibition of the independent enzyme activity, was observed with 0.1 mM adenosine 3':5'-monophosphate (cAMP) when 1 muM cGMP was employed as a substrate.
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000302:isolation & purification* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D000242:Cyclic AMP / Q000494:pharmacology; D004355:Drug Stability; D006801:Humans; D007700:Kinetics; D009124:Muscle Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D009206:Myocardium / Q000737:chemistry / Q000201:enzymology*; D013552:Swine / Q000378:metabolism*
chemical_list: D009124:Muscle Proteins; D000242:Cyclic AMP; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D002118:Calcium