PubMed · 3002240
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M Freeling, D C Bennett. 1985. Maize Adh1.. https://doi.org/10.1146/annurev.ge.19.120185.001501
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The NAD(+)-dependent alcohol dehydrogenase (EC 1.1.1.1) from the thermoacidophilic archaebacterium Sulfolobus solfataricus, DSM1617 strain (SSADH), has been purified and characterized. Its gene has been isolated by screening two S. Solfataricus genomic libraries using oligonucleotide probes. The encoding sequence consists of 1041 base pairs, and it shows a high preference for codons ending in T or A. The primary structure, determined by peptide and gene analysis, consists of 347 amino acid residues, yielding a molecular weight of 37,588. A level of identity of 24-25% was found with the amino acid sequences of horse liver, yeast, and Thermoanaerobium brockii alcohol dehydrogenases. The coenzyme-binding and catalytic and structural zinc-binding residues typical of eukaryotic alcohol dehydrogenases were found in SSADH with the difference that one out of the four structural zinc-binding Cys residues is substituted by Glu. The protein contains four zinc atoms per dimer, two of which are removed by chelating agents with a concomitant loss of structural stability.
Ethanol is oxidized in the liver by three different enzyme systems, namely by alcohol dehidrogenase (ADH), the microsomal ethanol oxidizing system and catalase. Alcohol also undergoes a first pass metabolism in the gastric mucosa due to alcohol dehydrogenase. This first pass metabolism of ethanol is decreased in the alcoholic, in the fasted state, in the elderly and during cimetidine therapy leading to elevated alcohol blood-concentrations. Ethanol toxicity is closely related to its metabolism in the liver. Ethanol oxidation by ADH generates reducing equivalents (NADH) and acetaldehyde (AA). The elevated NADH/NAD ratio results in alterations of the intermediary metabolism of lipids, carbohydrates, proteins, purines, hormones and porphyrins. Furthermore, NADH flavours free radical production. The ethanol-associated redox changes are pronounced in the perivenular zone, since this is the area of low oxygen tension and of high ADH activity. In addition to NADH, AA exerts striking toxic effects on the hepatocyte. AA binds to cellular proteins and membranes including the mitochondria, microtubules, glutathion and various enzymes. In addition, AA and lactate stimulate collagen production in fibroblasts. AA-adducts stimulate the production of antibodies against AA-epitopes and could thus aggravate the liver injury. Chronic ethanol consumption results also in the microsomal induction of a specific ethanol-inducible form of cytochrome P--450, the cytochrome P--450IIE1 with high affinity not only to ethanol but also to some drugs (acetaminophen), procarcinogens (nitrosamines) and industrial agents (carbon tetrachloride). The interaction between ethanol metabolism and the metabolism of these compounds including vitamin A may also contribute to hepatic toxicity, since the susceptibility of the alcoholic toward those compounds is enhanced.
A gene (FDH1) of Candida maltosa which confers resistance to formaldehyde in Saccharomyces cerevisiae was cloned and its nucleotide sequence determined. The gene has a single intron which possesses the highly conserved splicing signals found in S. cerevisiae introns. We demonstrated that processing of the pre-mRNA of the cloned gene occurred identically in both S. cerevisiae and C. maltosa. The predicted amino acid sequence from the cloned gene showed 65.5% identity to human alcohol dehydrogenase (ADH) class III and 23.9% identity to S. cerevisiae ADH1. The most probable mechanism of resistance to formaldehyde is thought to be the glutathione-dependent oxidation of formaldehyde which is characteristic for ADH class III. The cloned FDH1 gene was successfully employed as a dominant selectable marker in the transformation of S. cerevisiae.