"Enzymogenesis": classical liver alcohol dehydrogenase origin from the glutathione-dependent formaldehyde dehydrogenase line.

Abstract

Analysis of the activity and structure of lower vertebrate alcohol dehydrogenases reveals that relationships between the classical liver and yeast enzymes need not be continuous. Both the ethanol activity of class I-type alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) and the glutathione-dependent formaldehyde activity of the class rI-type enzyme [formaldehyde:NAD+ oxidoreductase (glutathione-formylating), EC 1.2.1.1] are present in liver down to at least the stage of bony fishes (cod liver: ethanol activity, 3.4 units/mg of protein in one enzyme; formaldehyde activity, 4.5 units/mg in the major form of another enzyme).Structural analysis of the latter protein reveals it to be a typical class HI enzyme, with limited variation from the mammalian form and therefore with stable activity and structure throughout much of the vertebrate lineage. In contrast, the classical alcohol dehydrogenase (the class I enzyme) appears to be the emerging form, first in activity and later also in structure. The class I activity is present already in the piscine line, whereas the overall structural-type enzyme is not observed until amphibians and still more recent vertebrates. Consequently, the class I/I duplicatory origin appears to have arisen from a functional class HI form, not a class I form. Therefore, ethanol dehydrogenases from organisms existing before this duplication have origins separate from those leading to the "classical" liver alcohol dehydrogenases. The latter now often occur in isozyme forms from further gene duplications and have a high rate of evolutionary change. The pattern is, however, not simple and we presently find in cod the first evidence for isozymes also within a class Im alcohol dehydrogenase. Overall, the results indicate that both of these classes of vertebrate alcohol dehydrogenase are important and suggest a protective metabolic function for the whole enzyme system. ancestral lineages (15), apparently utilized to different extents in different organisms. The Drosophila line is now known to be part of another large protein family, short-chain dehydrogenases, encompassing also human prostaglandin and steroid dehydrogenases (16)(17)(18).Second, separate classes of human alcohol dehydrogenase were discovered (19). These classes have been structurally characterized and shown to typify mammalian alcohol dehydrogenases, with separate evolutionary properties (20). The explanation is a series ofgene duplications at different stages (21), generating a system of isozymes and enzymes, which have been studied for structure-function relationships (22,23).Third, analysis of amphibian alcohol dehydrogenase recently established a first estimate of the timing of one of the duplications that explain the classes. This timing placed the class I/III separation early in vertebrate development (24), and analysis of the ethanol-active cod enzyme showed this to be a protein with mixed-class properties (25). These results seemed puzzling, since both glutathione-dependent formaldehyde-active class III [...

Ascidian and Amphioxus Adh Genes Correlate Functional and Molecular Features of the ADH Family Expansion During Vertebrate Evolution

“…The expansion of single-copy genes in vertebrates has been dated in a variety of gene families (for reviews see Lundin 1993;Skrabanek and Wolfe 1998). Irrespective of the mechanism, duplications are responsible for the extant gene families and isoforms from fish to mammals (Ohno 1970;Lundin 1993) and are believed to be related to the gains in complexity which have allowed the acquisition of new functions through enzymogenesis (Danielsson and Jörnvall 1992) and changes in gene regulation (for a review see Shimeld 1999).…”

“…The class 1 enzyme, the "classical" ethanol-active form, has evolved rapidly and exhibits a considerable variability among species (Danielsson et al 1994a). ADH class 3 [glutathione-dependent formaldehyde dehydrogenase (Koivusalo et al 1989)] is present in prokaryotes and in all eukaryotes and appears to be the ancestral form from which the other vertebrate ADH classes emerged (Danielsson and Jörnvall 1992;Danielsson et al 1994a;Cañestro et al 2000) through gene duplications during early vertebrate radiation. Supporting evidence comes from the apparent absence of an ethanol-active class 1 form in lines originating before the bony fish (Danielsson et al 1994b) and the presence of a class 1/3-mixed form in bony fish (Danielsson et al 1992).…”

Diversity of Vertebrate Class I Alcohol Dehydrogenase

“…brates [6], apparently illustrating enzymogenesis of novel ethanol dehydrogenase activity from the ancient formaldehyde dehydrogenase [7]. At least four further classes of alcohol dehydrogenase exist, indicating still more gene duplications, giving rise to classes I1 [2], IV [S], V [9] and VI [lo], of which just a few variants are known, not allowing for extensive conclusions on their patterns of divergence.…”

Linking of Isozyme and Class Variability Patterns in the Emergence of Novel Alcohol Dehydrogenase Functions

“…4). In contrast, for class 111, w e thus far have only one reported isozyme pair (h/l) [6]. Therefore …”

“…Since conditions for traditional class and isozyme separations on ion exchangers did not produce separation of these forms, we decided to evaluate i sozyme differences by determination of the two isozyme primary structures in mixture. Although cumbersome and involving more work, this approach has the advantage of not risking loosing any forms, which has been a problem in other alcohol dehydrogenases of lower vertebrates, where initial studies also indicated isozymes which were difficult to separate, and where the presence of dimers in selective combinations were found [6].…”