Human alcohol dehydrogenase: structural differences between the beta and gamma subunits suggest parallel duplications in isoenzyme evolution and predominant expression of separate gene descendants in livers of different mammals.

Abstract

ABSTRACTlibman alcohol dehydrogenase (ADH; alcohol:NAD+ oxidoreductase, EC 1.1.1.1) occurs in multiple forms, which exhibit distinct electrophoretic mobilities and enzymatic properties. The homogeneous isoenzymes I3P, and y1yi were isolated from livers of Caucasians with "tyrpical" ADH phenotype by double ternary complex affinity chromatography and ion exchange chromatography. The differences between the PI and Vi subunits were determined by structural analysis of all tryptic peptides from the carboxymethylated proteins. The human f3I and Vi chains differ at 21 of the 373 positions (5.6%). Ten tryptic peptides account for the differences. All residue substitutions are compatible with one-base mutations and result in largely unaltered properties, but five lead to charge differences. Sixteen substitutions are at positions corresponding to the catalytic domain of the well-known horse enzyme; five correspond to the coepzyme-binding domain. Substitutions adjacent to important regions may correlate with differences in coenzyme binding, substrate specificities, and active-site relationships. The residue replacements between the PI and yV subunits of human ADH are not identical to the known substitutions between ethanol-active (E) and steroid-active (S) subunits of horse ADH. Thus, the duplication leading to human pi and yi subunits is separate and different from that leading to equine E and S subunits. Both duplications are likely to have occurred after the ancestral separation of human and equine ADH. Of the 21 residues that are different between P1I/ yi, 13 in y'but only 6 in flu are identical to those of the horse E chain. This suggests a closer relationship between yV and E, although .81 in mah and E in the horse are the subunits recovered in highest yield from liver ADH preparations. Consequently, in these two mammalian species, relative activities of genes for an isoenzyme family appear to be different.Human and horse alcohol dehydrogenases (ADH; alcohol:

Isozyme developments in mammalian class‐I alcohol dehydrogenase

“…Assuming constant evolutionary rates for the enzyme in all lines, the time for the primate radiation to cover = l o million years, and that for the mammalian radiation =70 million years, the horseline isozyme divergence would correspond to a time rougly 10 million years ago, while that for the human line would correspond to two duplications rougly 30 million years ago. The conclusion of isozyme duplications, multiple and more recent than lineage separations is in agreement with early suggestions from structural analyses [4] and with dating attempts for the duplications [27].…”

“…Isozyme versus species variations for mammalian class-I alcohol dehydrogenases. In the calculations of the species variations, the same or most similar isozymes have been used, thus the variation of human y type from the non-primate enzymes, explained by the relationships in [4], and human a and p, versus the corresponding monkey enzymes, respectively.…”

Chromosome assignment, biochemical and immunological studies on a human aldehyde dehydrogenase, ALDH3

“…The pattern of structural relationships emerging from the study of ALDH is not dissimilar to the situation found within the human alcohol dehydrogenases. Three distinct classes of ADH genes and gene products have been recognized and there is evidence for very close structural similarities within the largest class (I) comprising the ADHl, ADH2 and ADH3 loci (Vallee & Bazzone, 1983;Jornvall et al 1984;Buhler et al 1984;Duester et al 1984). Since the products of alcohol dehydrogenase activity, aldehydes, are the substrates for aldehyde dehydrogenase activity, one might expect some degree of parallelism, say in tissue distribution and substrate specificity, between these two types of dehydrogenase.…”

Review of Genetic and Biological Markers in Drug Abuse and Alcoholism.

“…A restriction map of this clone was derived by further digesting the isolated cDNA insert by various enzymes. Restriction fragments were then cloned into the M13 bacteriophage and sequenced (Duester et al 1984). Analysis of the DNA sequence of the insert in the pADH12 clone revealed that it contained a 593 base pair 3' untranslated region in addition to a 273 base pair translated region coding for 91 amino acids.…”

“…Information from peptide mapping studies (Strydom and Vallee 1982) and partial sequence information on the ADH3 polypeptide (Bühler et al 1984) indicate that the coding regions of the three class I ADH genes are closely homologous. Using radiolabeled pADH12 as a probe under conditions of low stringency, it should be possible to isolate from libraries of human genomic or cDNA, clones corresponding to all three class I ADH genes.…”