Alcohol dehydrogenase of class III: consistent patterns of structural and functional conservation in relation to class I and other proteins

Abstract

Class III alcohol dehydrogenase from the lizard Uromastix hardwickii has been characterized. This non-mammalian, gnathostomatous vertebrate class III form allows correlations of structures and functions of this class, the traditional class I alcohol dehydrogenase, and other well-studied proteins. Catalytically, results show similar recoveries and activities of all vertebrate class III forms independent of source, similar activities also in invertebrates but in lower amounts, and considerably higher specific activities in microorganisms. Structurally, variability patterns are consistent throughout the vertebrate system with a ratio in accepted point mutations versus class I of 0.4. This ratio between different classes of a zinc enzyme is comparable to that between different heme proteins (cytochrome c and myoglobin), suggesting defined but non-identical functions also for the alcohol dehydrogenase classes.Key words: Alcohol dehydrogenase; Reptilian protein; Uromastix hardwickii; Amino acid sequence; Molecular evolution absence of class I in species diverging before the supposed class III duplication [6,9], and presence of enzymes with class-mixed properties in species originating at that time (fish [10]).Although the alcohol dehydrogenase classes now constitute a model system with an apparent class III parent form and with repeated descendents from separate gene duplications, class III has not been characterized in any sub-mammalian traditional vertebrate (Superclass Gnathostomata). Many of the conclusions therefore depend on the recently characterized insect enzyme [6] and cannot be directly correlated with variants of class I which have been studied in sub-mammalian vertebrate lines. We have therefore analyzed the Uromastix class III alcohol dehydrogenase, bridging the gap between invertebrates and mammals. The results allow firm assignment of constant class III properties throughout vertebrates. They also allow correlations with other well-studied protein families, such as those of the heine proteins cytochrome c and myoglobin, relating, in extent of variability, to alcohol dehydrogenase of classes III and I, respectively.

Liver Class‐I Alcohol Dehydrogenase Isozyme Relationships and Constant Patterns in a Variable Basic Structure

“…Notably, the first five of these are fairly adjacent (tVDiK in a 50-odd segment) and may possibly be discerned even in fragment studies that involve forms only known in part. [14), and the class-111 enzyme from Urornczstix [15]. G. h. major, Geomys hurscirius incrjor; Details of residue variations.…”

“…38 major forms presently characterized are included, but not additional allelic and strain variants. Data from data banks except for the recent reports of the class-I enzymes from kiwi [I31 and Urornastiw 181, the class-I1 enzyme from ostrich[14), and the class-111 enzyme from Urornczstix[15]. G. h. major, Geomys hurscirius incrjor; beyond C-terminus of the human V enzyme); empty space, sequence not determined (Mallard).…”

An ethanol‐inducible MDR ethanol dehydrogenase/acetaldehyde reductase in Escherichia coli

“…Peptides were generated by proteolytic digestion with Lys‐C protease, Glu‐C protease and Asp‐N protease (all from Boehringer Mannheim) at 37 °C overnight with enzyme/protein ratios of 1 : 25–1 : 100 in 0.1 m ammonium bicarbonate, pH 8.1, with 2 m urea, and by CNBr cleavage in 70% formic acid for 24 h at room temperature. The peptides obtained were purified by reverse‐phase HPLC on Vydac C18 (2.4 mm × 25 cm) and elution with a gradient of acetonitrile in 0.1% trifluoroacetic acid [4]. The amino acid compositions were determined using a Pharmacia AlphaPlus analyzer after acid hydrolysis in 6 m HCl for 24 h at 110 °C.…”

“…Alcohol dehydrogenases of the zinc metalloenzyme medium‐chain dehydrogenase/reductase (MDR) family occur in essentially all types of life form [1]. The class III form, with little or almost no ethanol activity, but with identity to glutathione‐dependent formaldehyde dehydrogenase [2], appears to be an original form and has been characterized in vertebrates [3,4], invertebrates [1,5], plants [6,7], fungi [8–10] and prokaryotes [11,12]. However, other ethanol‐active MDR enzyme forms also occur at several stages and appear to reflect functional convergence [13] from separate duplicatory events, as deduced for plant (class P enzyme) and animal (class I enzyme) ethanol dehydrogenases [6,7].…”

S-Nitrosoglutathione is a substrate for rat alcohol dehydrogenase class III isoenzyme

“…ADH class III isoenzyme is a ubiquitous enzyme found in a host of animal and plant species [50,51]. mRNA representing this enzyme has been detected in the full range of rat tissues considered [52].…”