Simian liver alcohol dehydrogenase: isolation and characterization of isoenzymes from Saimiri sciureus

The alcohol dehydrogenase (ADH) of squirrel monkey liver can be purified and separated into pyrazole-insensitive and pyrazole-sensitive isoenzymes by affinity chromatography. This is the first demonstration of two functionally distinct classes of ADH in a species other than man. The inhibition of the two enzyme fractions by 4-methylpyrazole is analogous to that observed for the corresponding isoenzymes of human liver. Similarly, the substrate specificity of the pyrazole-insensitive form is more limited and its Km for ethanol (4 mM at pH 7.5) and acetaldehyde (11 mM at pH 7.0) is larger than that of the pyrazole-sensitive isoenzymes. However, their physicochemical and compositional characteristics, i.e., molecular weight, zinc content, and dimeric structure, are all virtually identical with those of other mammalian alcohol dehydrogenases studied thus far. Zinc is essential for the enzymatic function of both molecular forms as demonstrated by inhibition with chelating agents.