Virus of Avian Erythromyeloblastic Leukosis. VI. Properties of the Enzyme Associated with the Virus in Dephosphorylating Adenosine Triphosphate2

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Abstract
Studies were made on the properties of the adenosine triphosphatase activity associated with the virus of erythromyeloblastic leukosis in the blood plasma from diseased chicks. The behavior of the material was typically that of an enzyme. Dephosphorylation was proportional to the volume of virus-containing plasma studied, and the activity was specific and limited to hydrolysis of the terminal phosphate of the substrate. Under suitable conditions hydrolysis approached closely the theoretical endpoint yielding equivalent amounts of free phosphate and adenosine diphosphate. The latter product was unaffected by hydrolysis or dismutation, and no alteration was observed in adenylic acid added to the system. Dephosphorylation was activated equally by Ca++ or Mg++, separately or together, in the presence of either or both K+ and Na+. Chelation with versene eliminated the effects of the divalent ions. There was a single sharp peak at the pH optimum of activity of 7.16.