Abstract
Ecto-5'-nucleotidase (ecto-5'-NU) of platelets was enhanced by concanavalin A (Con A). This effect of Con A was antagonized by α-methyl-D-mannose, a specific antagonist of Con A binding to glycoprotein. Coformycin, an adenosine deaminase inhibitor, did not change the effect of Con A on the ecto-5'-NU. Uptake of adenosine by platelets was not affected by Con A. It was suggested that the ecto-5'-NU of platelet might be a direct and primary site of action of Con A.
