Loss of the characteristic features of atypical human liver alcohol dehydrogenase during purification

In 1965 an typical human liver alcohol dehydrogenase was described to be present in two histologically normal autopsy livers by von Wartburg, et al. (1). The atypicality of this new enzyme was not based on different electrophoretic mobilities from normal alcohol dehydrogenase, a feature which has identified genetic variants of other enzymes such as the lactic dehydrogenases (2,3), but it was solely based on differing in-vitro kinetic findings. These differences were: (1) a pH maximum for ethanol oxidation of 8.5 for atypical enzyme as compared with 10.8 for the normal enzyme, (2) a higher specific activity at pH 8.8 for the atypical enzyme, (3) thiourea inhibition at pH 8.8 of the atypical enzyme but activation of the normal enzyme and (4) some variation in optimal substrate concentration and inhibition of activities by excess substrate with certain alcohols. The present study emphasizes the many similarities between normal and atypical alcohol dehydrogenase, and demonstrates the loss of atypical features from the variant enzyme during purification.