Activation of wheat germ acetyl CoA carboxylase by potassium and rubidium.

Wheat germ acetyl CoA carboxylase requires certain alkali cations to exhibit maximal activity. Maximal activation results when 60 mM K⁺ or Rb⁺ are included in the assay mixture, whereas only marginal activation occurs in the presence of similar concentrations of Li⁺⁺ and Na⁺⁺. Cs⁺⁺ activates, but less effectively than K⁺ or Rb⁺. Since it is also possible to activate the enzyme maximally using 20 mM potassium isocitrate, but not 20 mM sodium isocitrate, activation of the wheat germ enzyme is due to a cation effect and not to citrate anion.