title: Effects of spermine on activity and stability of calcium-dependent guanosine 3',5'-monophosphate phosphodiesterase.
abstract: Spermine in micromolar concentrations decreased the basal activity of a guanosine 3',5'-monophosphate (cGMP) phosphodiesterase from bovine brain but had no effect in the presence of Ca2+ plus the calcium-dependent regulatory protein (CDR) which increased the activity of the enzyme 4- to 6-fold. Similar effects of spermine were observed on the enzyme at several stages of purification. Spermidine and putrescine were also inhibitory but higher concentrations were required. In the absence of Ca2+ and CDR, the enzyme exhibited two apparent Km values for cGMP (2.5 and 20 microM) which were unaltered by spermine. In the presence of Ca2+ and CDR (when spermine had no effect on activity), a single Km (3.5 microM) was observed. Enzyme purified by chromatography on CDR-Sepharose was rapidly inactivated during incubation at 30 degrees C in 5 mM potassium phosphate buffer (pH 7.0) with EDTA and ethylene glycol bis(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA). Spermine (20 microM) partially stabilized enzyme activity under these conditions, although it was somewhat less effective than 2 mM MgCl2. The inhibitory effects of spermine (or other polyamines) on basal phosphodiesterase activity, which can be overcome by Ca2+ and CDR, could be important in the regulation of cellular cyclic nucleotide content.
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D004355:Drug Stability; D004789:Enzyme Activation; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D011700:Putrescine / Q000494:pharmacology; D013095:Spermidine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology*
chemical_list: D013096:Spermine; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D008274:Magnesium; D002118:Calcium; D013095:Spermidine; D011700:Putrescine