Alcohol and polyol dehydrogenases.

"Long" and "short" alcohol dehydrogenases with different structures and catalytic mechanisms exist and the same sub-grouping appears to apply to polyol dehydrogenases. Mammalian liver sorbitol dehydrogenase is clearly related to "long" alcohol dehydrogenases and has structural properties intermediate between those of mammalian and yeast alcohol dehydrogenases. The amino acid sequence of a large segment of the N-terminal part of a liver sorbitol dehydrogenase is now determined and shown to be strictly homologous with the long alcohol dehydrogenases. Seventeen of 93 positions have identical residues among all enzymes compared, defining residues of particular functional significance. Proline and glycine residues suggest largely similar conformations between N-terminal parts of sorbitol dehydrogenase and "long" alcohol dehydrogenases, cysteine and histidine residues suggest a conserved zinc atom at the active site, and other residues correlate with structures of special importance.