[Effect of ions on determination of 3',5'-AMP by the method of saturation]

The effects of La2+, Pb2+, Ba2+, Zn2+, Ca2+, Mg2+, Mn2+, NH+4 in concentrations of 10(-7), 10(-5), 10(-3) M were studied as applied to the protein binding of cyclic 3' : 5' = AMP. It is shown that Ba2+, La2+, Pb2+ increase the binding, while Zn2+ has no effect, and Mn2+, NH+4 decrease the binding of 3' : 5' = AMP. The effects of Ca2+ and Cd2+ were dependent on the concentration. The maximal binding in the presence of Ca2+ and Cd2+ was observed at a concentration of 10(-5) M and 10(-3) M, respectively. It is suggested that Mg2+ and Ca2+ take part in the regulation of cyclic AMP binding with proteinkinase in vivo.