Expression and kinetic characterization of recombinant human stomach alcohol dehydrogenase. Active-site amino acid sequence explains substrate specificity compared with liver isozymes.

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Citation

Kedishvili NY, Bosron WF, Stone CL, Hurley TD, Peggs CF, Thomasson HR, Popov KM, Carr LG, Edenberg HJ, Li TK

Expression and kinetic characterization of recombinant human stomach alcohol dehydrogenase. Active-site amino acid sequence explains substrate specificity compared with liver isozymes.

J Biol Chem. 1995 Feb 24;270(8):3625-30.

PubMed ID
7876099 [ View in PubMed
]
Abstract

A full-length 1966-base pair clone of the human class IV alcohol dehydrogenase (sigma-ADH) was isolated from a human stomach cDNA library. The 373-amino acid sigma-ADH encoded by this cDNA was expressed in Escherichia coli. The specific activity of the recombinant enzyme for ethanol oxidation at pH 7.5 and 25 degrees C, calculated from active-site titration of NADH binding, was 92 +/- 9 units/mg. Kinetic analysis of the catalytic efficiency (kcat/KM) of recombinant sigma-ADH for oxidation of primary alcohols indicated broad substrate specificity. Recombinant human sigma-ADH exhibited high catalytic efficiency for oxidation of all-trans-retinol to all-trans-retinal. This pathway is important in the synthesis of the transcriptional regulator all-trans-retinoic acid. Secondary alcohols and 3 beta-hydroxysteroids were inactive with sigma-ADH or were oxidized with very low efficiency. The KM of sigma-ADH for ethanol was 25 mM, and the KM for primary straight chain alcohols decreased substantially as chain length increased. There are important amino acid differences in the alcohol-binding site between the human class IV (sigma) and human class I (beta) alcohol dehydrogenases that appear to explain the high catalytic efficiency for all-trans-retinol, the high kcat for ethanol, and the low catalytic efficiency for secondary alcohols of sigma-ADH relative to beta 1-ADH. For example, modeling the binding of all-trans-retinol in the human beta 1-ADH structure suggested that coordination of retinol to the active-site zinc is hindered by a loop from residues 114 to 120 that is at the entrance to the alcohol-binding site. The deletion of Gly-117 in human sigma-ADH and a substitution of Leu for the bulky Tyr-110 appear to facilitate retinol access to the active-site zinc.

DrugBank Data that Cites this Article

Polypeptides
NameUniProt ID
Alcohol dehydrogenase class 4 mu/sigma chainP40394Details