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Purification and Partial Amino Acid Sequence of a High‐Activity Human Stomach Alcohol Dehydrogenase
Author(s) -
Stone Carol L.,
Thomasson Holly R.,
Bosron William F.,
Li TingKai
Publication year - 1993
Publication title -
alcoholism: clinical and experimental research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.267
H-Index - 153
eISSN - 1530-0277
pISSN - 0145-6008
DOI - 10.1111/j.1530-0277.1993.tb00863.x
Subject(s) - isozyme , alcohol dehydrogenase , isoelectric focusing , biochemistry , amino acid , peptide sequence , enzyme , biology , ethanol , microbiology and biotechnology , chemistry , gene
To understand the relative importance of alcohol dehydrogenase (ADH) isoenzymes in gastric ethanol metabolism, a stomach‐specific ADH (σ‐ADH) was purified to homogeneity from human transplant donor and surgical tissues, and its activity for ethanol oxidation was examined. The enzyme from these tissues had a specific activity at pH 10 of ˜70 units/mg, about 10 times that reported by Moreno and Parés ( J. Biol. Chem. 266:1128–1133, 1991). The enzyme exhibited a high K m for ethanol at pH 7.5 and 10 (29 and 5.2 mM, respectively). This high‐activity α‐ADH isoenzyme migrated on starch and isoelectric focusing gels to a position slightly anodic to the liver σ isoenzyme. It was subjected to digestion by endoproteinases, and ˜40% of the protein was sequenced. The σ‐ADH exhibited 75%, 68%, and 62% sequence identity to the human class I ( β 1 ), II (π), and III (χ) isoenzymes, respectively, and 61% identity to the deduced ADH6 amino acid sequence. Phylogenetic analysis indicated that precursors to this high‐activity σ‐ADH and the class I isoenzymes diverged more recently than precursors to the class II and III isoenzymes, after reptilian and avian divergence. The high‐activity σ‐ADH isoenzyme therefore represents a distinct class of ADH (class IV), more closely related in evolution to the class I isoenzymes than to the other known human isoenzymes.