Interaction of Eu3+ with yeast alcohol dehydrogenase

The activity of yeast alcohol dehydrogenase is markedly enhanced by Eu3+ ions. At pH 7.0 two binding constants for Eu3+, 1.0x10(-2) and 2.0x10(-3) microM, were obtained using a Scatchard plot. The presence of Zn2+ ions restricts the Eu3+ -induced increase in the activity of yeast alcohol dehydrogenase. Studies on the tryptophan fluorescence of the enzyme in the absence and presence of Eu3+ or Zn2+ ions showed that Eu3+ affects tertiary or quaternary structures, which is consistent with its activation of the enzyme. The presence of Zn2+ reverses the conformational changes caused by Eu3+. Comparison of the effects of Eu3+ with Zn2+ for apo-yeast alcohol dehydrogenase indicates that their binding sites on the protein are different.