[Influence of twovalent foreign cations on the uptake of zinc by Chlorella (author's transl)].

The influence of 10(-4) divalent cations on the uptake of labelled Zn in the concentration range 10(-5) to 5 x 10(-5) M into the interior of Chlorella fusca at 30 degrees C was measured during 75 min. The Zn absorbed on the surface or contained in the free space was removed by washing with EDTA. Corrections were applied for the loss in concentration due to surface adsorption, etc. The results were consistent with competitive inhibition of Zn uptake by the foreign ions. No allosteric inhibition was found. From the Lineweaver-Burk diagram, for uninhibited Zn, KM was found as 7 x 10(-6) M and Vmax as 8.3 x 10(-9) mol.min-1.g-1 algae. The inhibitor constants were: Mg 1.3 x 10(-5), Ca 4.3 x 10(-5), Co 4.3 x 10(-5), Ni 4.3 x 10(-5), Cd 1.3 x 10(-5) and Pb 9.4 x 10(-7) M. The values given for Km and the inhibitor constant refer to the velocities of uptake after 45 min.