Ca²⁺ Dependency of Diadenosine 5', 5'''-p¹, p⁴-Tetraphosphate Degradation in Dog Plasma

Abstract

Diadenosine 5', 5'''-p¹, p⁴-tetraphosphate (Ap4A) degradation in dog plasma was inhibited by the addition of EDTA. The Ap4A degrading activity seemed to be recovered by the addition of metal ions, Ca²⁺, Co²⁺, Cu²⁺, Mg²⁺, Mn²⁺ or Zn²⁺ to plasma in which the activity was lost by the addition of EDTA. Especially, the degradation was accelerated by the addition of Ca²⁺ to the plasma, and the degradation rate was dependent on the concentration of Ca²⁺. The results of this study suggested that the enzymatic degradation of Ap4A in dog plasma was modulated by the concentration of Ca²⁺.