[Allosteric modification of adenylate deaminase activity: appearance of adenosine deaminase activity as an effect of potassium ions].

The activation of purified adenylate deaminase from the duck myocardium by K+ is accompanied by modification of the substrate specificity and by the appearance of the capacity to deaminate adenosine and adenine. Adenosine deaminase activity originates at the concentration of K+ of 0.15 M that possesses the most stimulating effect on adenylate deaminase activity; with the increase of potassium ions concentration adenosine deaminating activity is enhanced as well, with a parallel reduction of Hill's constant. The PH-dependence, mode of inhibition by phosphate ions and the effect of alkaline metals suggests that adenosine deamination is carried out by natural adenylate deaminase active centres when their conformation is changed under the activator action.