Stereospecific oxidation of secondary alcohols by human alcohol dehydrogenases.
The human liver alpha alpha alcohol dehydrogenase exhibits a different substrate specificity and stereospecificity for secondary alcohols than the human beta 1 beta 1, and gamma 1 gamma 1 or horse liver alcohol dehydrogenases. All of the enzymes efficiently oxidize primary alcohols, but alpha alpha oxidizes secondary alcohols far more efficiently than human beta 1 beta 1 and gamma 1 gamma 1 or horse liver alcohol dehydrogenase. Specifically, alpha alpha oxidizes four- and five-carbon secondary alcohols with efficiencies 0.06-2.2 times that of primary homologs and oxidizes these secondary alcohols with efficiencies up to 3 orders of magnitude greater than those of the three other isoenzymes. Whereas the human beta 1 beta 1, gamma 1 gamma 1 and horse isoenzymes show a distinct preference toward (S)-(+)-3-methyl-2-butanol, the alpha alpha isoenzyme prefers (R)-(-)-3-methyl-2-butanol. Computer-simulated graphics demonstrate that the horse subunit accommodates (S)-(+)-3-methyl-2-butanol within the active site much better than the opposite stereoisomer, primarily due to steric hindrance caused by Phe-93. Human alpha may accommodate (R)-(-)-3-methyl-2-butanol better than (S)-(+)-3-methyl-2-butanol because of close contacts between the latter and Thr-48. These observations suggest that substitutions at positions 93 and 48 in the active site of human liver alcohol dehydrogenase isoenzymes may determine their substrate specificity for secondary alcohols.
Stone
C L
CL
Department of Biochemistry, Indiana University School of Medicine, Indianapolis 46223.
Li
T K
TK
Bosron
W F
WF
D000426:Alcohol Dehydrogenase / Q000378:metabolism*; D000438:Alcohols / Q000378:metabolism*; D001665:Binding Sites; D000440:Butanols / Q000378:metabolism; D003511:Cyclohexanols / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D010084:Oxidation-Reduction; D000439:Pentanols / Q000378:metabolism; D013237:Stereoisomerism; D013379:Substrate Specificity
D000438:Alcohols; D000440:Butanols; D003511:Cyclohexanols; D007527:Isoenzymes; D000439:Pentanols; D000431:Ethanol; C040507:isobutyl alcohol; C029683:isopentyl alcohol; D000426:Alcohol Dehydrogenase