Purified horse-liver alcohol dehydrogenase is heterogeneous on starch-gel electrophoresis in several buffer systems. 2. The electrophoretic pattern is altered by the addition to the buffers of oxidized or reduced coenzymes, isobutyramide, metal ions or metal-chelating agents. 3. The effect of coenzymes on the pattern suggests that the major cause of the observed heterogeneity is not the existence of isoenzymes, but the presence in the enzyme preparations of coenzyme-enzyme complexes or complexes with other nucleotides similar to, but less reactive than, the coenzymes. 4. Metal ions and chelating agents influence the electrophoretic separation by partial denaturation and inactivation of the enzyme.
