Zinc in horse liver alcohol dehvdrogenase.

The alcohol dehydrogenase (ADH’) of yeast has twice the molecular weight of the ADH of horse liver (l), contains 4 gm. atoms of zinc (2), and binds 4 moles of DPN per mole of protein (1). The liver ADH binds 2 moles of coenzyme per mole (3). These facts prompted the prediction that the liver ADH should contain 2 gm. atoms of zinc per mole of protein (2). The presence of 2 atoms of zinc in liver ADH has been briefly reported (4,5). This paper presents detailed spectrographic, microchemical, and polarographic analyses which demonstrate the presence of 2 atoms of zinc per molecule of liver ADH; all other metals are removed during purification. The activity of the enzyme can be modified in a manner analogous to but not identical with that observed for other zinc dehydrogenases.