CLASS-IV ALCOHOL-DEHYDROGENASE (THE GASTRIC ENZYME) - STRUCTURAL-ANALYSIS OF HUMAN SIGMA-SIGMA-ADH REVEALS CLASS-IV TO BE VARIABLE AND CONFIRMS THE PRESENCE OF A 5TH MAMMALIAN ALCOHOL-DEHYDROGENASE CLASS

Human gastric alcohol dehydrogenase (sigma-sigma-ADH) was submitted to peptide analysis at picomole scale. A total of 72 positions were determined in the protein chain, providing information on three aspects of alcohol dehydrogenase structures in general. First, the data establish the presence of a unique class of the enzyme, now confirmed as class IV, expressed in gastric tissue and separate from another novel class, now termed class V. Second, the class IV gastric enzyme has active site relationships compatible with an ethanol-active, zinc-containing alcohol dehydrogenase. Third, this enzyme class is of the variable type, like that for the 'variable', classical liver alcohol dehydrogenase of class I, and in contrast to that for the 'constant' class III enzyme. Known human alcohol dehydrogenase structures now prove the presence of at least seven human genes for the enzyme and nine for the whole protein family.