Structural and functional divergence of class II alcohol dehydrogenase--cloning and characterisation of rabbit liver isoforms of the enzyme

Eur J Biochem. 1998 Jan 15;251(1-2):236-43. doi: 10.1046/j.1432-1327.1998.2510236.x.


cDNAs coding for class II alcohol dehydrogenase were isolated from a rabbit-liver cDNA library. Deduced amino acid sequences show that isozymic forms of rabbit class II alcohol dehydrogenase exist, with a positional identity of 88.4%. A high variability in structure of class II alcohol dehydrogenase between the species is also reflected in function. The rabbit II-1 isozyme shows common characteristics with the human enzyme, but has a lower Km value for ethanol, 4.2 mM. The II-2 isozyme shows restriction for aliphatic alcohols longer than pentanol. For shorter alcohols the II-2 form has similar Km values as the II-1 isozyme, 5.5 mM for ethanol, but is a low activity variant with a 10-fold decrease in k(cat) values compared with II-1. Nevertheless, II-2 has a higher specificity for benzoquinone than II-1 due to a lower Km value, 80 microM compared with 1 mM, and is in this sense more like the human class II enzyme. In addition a rabbit class III alcohol dehydrogenase cDNA was isolated that encodes a typical class III enzyme/glutathione-dependent formaldehyde dehydrogenase. The finding of isozymic forms of class II alcohol dehydrogenase is in line with the evolution of the system of medium-chain alcohol dehydrogenases with different enzymes, different classes and different isozymes and further underline the complexity of the entire mammalian alcohol dehydrogenase system.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alcohol Dehydrogenase / genetics*
  • Alcohol Dehydrogenase / immunology
  • Alcohol Dehydrogenase / metabolism*
  • Aldehyde Oxidoreductases / genetics
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cloning, Molecular
  • Humans
  • Immunoblotting
  • Isoenzymes
  • Liver / enzymology*
  • Molecular Sequence Data
  • Rabbits
  • Sequence Homology, Amino Acid


  • Isoenzymes
  • Alcohol Dehydrogenase
  • formaldehyde dehydrogenase (glutathione)
  • Aldehyde Oxidoreductases

Associated data

  • GENBANK/AJ002388
  • GENBANK/AJ002389
  • GENBANK/Y15406