Purification and partial amino acid sequence of a high-activity human stomach alcohol dehydrogenase.
To understand the relative importance of alcohol dehydrogenase (ADH) isoenzymes in gastric ethanol metabolism, a stomach-specific ADH (sigma-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 approximately 70 units/mg, about 10 times that reported by Moreno and Parés (J. Biol. Chem. 266:1128-1133, 1991). The enzyme exhibited a high Km for ethanol at pH 7.5 and 10 (29 and 5.2 mM, respectively). This high-activity sigma-ADH isoenzyme migrated on starch and isoelectric focusing gels to a position slightly anodic to the liver pi pi isoenzyme. It was subjected to digestion by endoproteinases, and approximately 40% of the protein was sequenced. The sigma-ADH exhibited 75%, 68%, and 62% sequence identity to the human class I (beta 1), II (pi), and III (chi) isoenzymes, respectively, and 61% identity to the deduced ADH6 amino acid sequence. Phylogenetic analysis indicated that precursors to this high-activity sigma-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 sigma-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.
Stone
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CL
Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202-5122.
Thomasson
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HR
Bosron
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Li
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TK
D000328:Adult; D000426:Alcohol Dehydrogenase / Q000302:isolation & purification*; D000595:Amino Acid Sequence; D005075:Biological Evolution; D005753:Gastric Mucosa / Q000201:enzymology*; D006801:Humans; D007527:Isoenzymes / Q000302:isolation & purification*; D013274:Stomach Neoplasms / Q000201:enzymology; D014019:Tissue Donors
D007527:Isoenzymes; D000426:Alcohol Dehydrogenase