Activation of adenosine cyclic 3',5'-monophosphate phosphodiesterase by calcium ion and a protein activator

Autor:	George I. Drummond, R. D. Wickson, R. J. Boudreau
Rok vydání:	1975
Předmět:	chemistry.chemical_classification Activator (genetics) chemistry.chemical_element Phosphodiesterase Calcium PDE1 Biochemistry EGTA chemistry.chemical_compound Enzyme activator Enzyme chemistry Biophysics Cyclic adenosine monophosphate
Zdroj:	Biochemistry. 14:669-675
ISSN:	1520-4995 0006-2960
DOI:	10.1021/bi00675a004
Popis:	3',5'-CAMP phosphodiesterase was partially purified from bovine cerebral cortex. A heat-stable activating factor was separated from the enzyme by chromatography on DEAE-cellulose. The enzyme in crude ammonium sulfate fractions was stimulated by 5 mM CaCl2. This stimulation was reversed by the calcium chelator EGTA. The main phosphodiesterase peak obtained by DEAE-cellulose chromatography was not stimulated by Ca2+. Upon addition of column effluent containing a heat stable factor, Ca2+ activation was restored. Protein activator was inactive when endogenous contaminating Ca2+ was complexed with EGTA. It was concluded that activation of phosphodiesterase requires the presence of both activator and Ca1+. From an analysis of activation of cGMP hydrolysis a kinetic model for the interaction of Ca2+ and protein activator with the phosphodiesterase was developed. Heterotropic cooperativity between the binding of Ca2+ and protein activator to the phosphodiesterase was observed, i.e., Ca1+ decreased the apparent dissociation constant for protein activator and protein activator decreased the apparent dissociation constant for Ca2+.
Databáze:	OpenAIRE
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