Inhibition of Adenosine Triphosphatase Activity of the Plasma Membrane Fraction of Oat Roots by Diethylstilbestrol 1

AUTOR(ES)

Balke, Nelson E.

RESUMO

Diethylstibestrol (DES) inhibited noncompetitively the ATPase in the plasma membrane fraction from Avena sativa L. cv. Goodfield roots when assayed in the presence of MgSO4 or MgSO4 plus KCl. In the presence of MgSO4, 7.1×10−5 molar DES inhibited the enzyme 50%; whereas in the presence of MgSO4 and KCl, 1.3×10−4 molar DES was required for the same inhibition. Dixon plots indicated that in the presence of MgSO4, one molecule of DES bound to one molecule of ATPase; however, in the presence of MgSO4 and KCl, two or more molecules bound to one ATPase molecule. These results suggested that KCl causes a conformational change in the enzyme which exposes additional binding sites for DES, but that these sites are not as inhibitory as the first binding site.

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