| Alcohol Dehydrogenase |
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Alcohol dehydrogenases are a group of Dehydrogenase Enzyme s that occur in many organisms and facilitate the conversion between Alcohol s and Aldehyde s or Ketone s. In Human s and many other Animal s, they serve to break down alcohols which could otherwise be toxic; in Yeast and many Bacteria they Catalyze the opposite reaction as part of Fermentation . The EC Number of alcohol dehydrogenases is ; their CAS Number is 9031-72-5. IN HUMANS In humans, the enzyme is contained in the lining of the Stomach and in the Liver . It catalyzes the Oxidation of Ethanol to Acetaldehyde : :CH3CH2OH + NAD+ → CH3CHO + NADH + H+ This allows the consumption of Alcoholic Beverage s, but its original purpose is probably the breakdown of alcohols naturally contained in foods or produced by Bacteria in the Digestive Tract . Alcohol dehydrogenase is also involved in the toxicity of other types of alcohol: for instance, it oxidizes group of the alcohol in place. IN YEAST AND BACTERIA In resulting from Glycolysis is converted to acetaldehyde and Carbon Dioxide , and the acetaldehyde is then reduced to ethanol by alcohol dehydrogenase. The purpose of this latter step is the regeneration of NAD+, so that the energy generating glycolysis can continue. Humans exploit this process to produce alcoholic beverages, by letting yeast ferment various fruits or grains. The main alcohol dehydrogenase in yeast is larger than the human one, consisting of four rather than just two subunits. It also contains zinc at its catalytic site. It is clear that the human and yeast alcohol dehydrogenases are closely related. INSECTS In Insect s such as the Fruit Fly , the alcohol dehydrogenase is smaller than in humans, does not contain a metal, and appears to be unrelated. IRON CONTAINING A third class of alcohol dehydrogenases, unrelated to the above two, are Iron containing ones. They occur in bacteria, and an (apparently inactive) form has also been found in yeast. IN FUEL CELLS The enzyme can be used to catalyze the breakdown of fuel for an ethanol Fuel Cell . Scientists at Saint Louis University used carbon-supported alcohol dehydrogenase with poly( Methylene Green ) as an annode, with a Nafion membrane, to achieve about 50 μ A /cm2 {Link without Title} . EXTERNAL LINKS
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