Adenylate Deaminase

Alkali metal ions activate adenylate deaminase from calf brain by increasing the apparent affinity of the enzyme for AMP. The enzyme is inhibited, but not inactivated, at high ionic strength. Inhibition of the enzyme by guanosine triphosphate is reversed by lithium ions, and less well by sodium ions. Potassium ions cause only a slight reversal of the GTP inhibition, and this only at relatively high concentrations. GTP decreases the apparent affinity of the enzyme for lithium ions. Alkali metal ions have little or no effect on the inhibition of the enzyme by iso-AMP. Magnesium ions are not required for the activation of the enzyme by ATP or for its inhibition by GTP. For a given concentration of ATP there is a range of magnesium ion concentrations over which the apparent affinity of the enzyme for AMP is increased.