Physical and enzymatic properties of a class III isozyme of human liver alcohol dehydrogenase: .chi.-ADH

chi-Alcohol dehydrogenase (chi-ADH), a class III isozyme characterized by its anodic electrophoretic mobility and lack of inhibition by 4-methylpyrazole, has been isolated from human liver and purified to homogeneity in a reducing medium. chi-ADH resembles other human liver ADH isozymes of classes I...

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Bibliographic Details
Published in:Biochemistry (Easton) 1984-05, Vol.23 (10), p.2193-2199
Main Authors: Wagner, Fred W, Pares, Xavier, Holmquist, Barton, Vallee, Bert L
Format: Article
Language:English
Subjects:
Alcohol Dehydrogenase
Alcohol Oxidoreductases - metabolism
Amino Acids - analysis
Analytical, structural and metabolic biochemistry
Animals
Biological and medical sciences
Electrophoresis, Starch Gel
Enzymes and enzyme inhibitors
Fundamental and applied biological sciences. Psychology
Horses
Humans
Hydrogen-Ion Concentration
Isoenzymes - metabolism
Liver - enzymology
Molecular Weight
NAD - metabolism
Oxidoreductases
Phenanthrolines - pharmacology
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Summary:chi-Alcohol dehydrogenase (chi-ADH), a class III isozyme characterized by its anodic electrophoretic mobility and lack of inhibition by 4-methylpyrazole, has been isolated from human liver and purified to homogeneity in a reducing medium. chi-ADH resembles other human liver ADH isozymes of classes I and II with respect to its molecular weight, dimeric structure, stoichiometry of zinc and NADH binding, and pH optima for the oxidation of alcohols. This homodimer exhibits subtle differences in its absorption spectrum and amino acid composition relative to those of other human isozymes but differs markedly from their specificity toward alcohols and aldehydes. chi-ADH oxidizes ethanol very poorly. The reaction is bimolecular, and an apparent Km cannot be discerned up to 2.3 M ethanol. The enzyme is inactive toward methanol, ethylene glycol, digitoxigenin, digoxigenin, and gitoxigenin , but alcohols with carbon chain lengths greater than four are oxidized rapidly with Km values decreasing with increasing carbon chain length. Taken jointly, the composition, structure, and enzymatic properties of the ADH isozymes purified and studied so far strongly imply that their metabolic roles, yet to be discovered, will give a new perspective to ethanol metabolism and pathology.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00305a014