Human alcohol dehydrogenase: dependence of secondary alcohol oxidation on the amino acids at positions 93 and 94.
The human liver alpha alpha and beta 1 beta 1 isoenzymes are straight-chain alcohol dehydrogenases with different efficiencies toward secondary alcohols. Two of the 24 amino acid substitutions in alpha alpha (A for F93 and I for T94) were made by site-directed mutagenesis of beta 1 beta 1 and the substrate specificity of beta 93A94I was examined. The Vmax/KM values of beta 93A94I for secondary alcohols (especially R enantiomers) are similar to that of alpha alpha and as much as 4000-fold greater than beta 1 beta 1, but the dependences of Vmax/KM on primary alcohol chain length are similar to beta 1 beta 1, but not alpha alpha. Thus, the substitutions of A for F93 and I for T94 in beta 1 beta 1 account for the increased efficiency towards secondary alcohols and stereoselectivity for enantiomeric alcohols, but not for the effects of chain length on the Vmax/KM for primary alcohols seen with alpha alpha.
Hurley
T D
TD
Department of Biochemistry and Molecular Biology, Indiana University Medical School, Indianapolis 46202-5122.
Bosron
W F
WF
D000426:Alcohol Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D000438:Alcohols / Q000378:metabolism*; D001665:Binding Sites; D006801:Humans; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013237:Stereoisomerism; D013379:Substrate Specificity
D000438:Alcohols; D007527:Isoenzymes; D011994:Recombinant Proteins; D000426:Alcohol Dehydrogenase