alcohol dehydrogenase

(noun)

A group of six enzymes that metabolize alcohol.

Related Terms

Examples of alcohol dehydrogenase in the following topics:

  • Absorption of Alcohol

    • Alcohol is metabolized (by alcohol dehydrogenase enzymes made in the liver) when it is absorbed into the bloodstream.
    • Alcohol is metabolized mainly by the group of six enzymes collectively called alcohol dehydrogenase.
    • The enzyme acetaldehyde dehydrogenase then converts the acetaldehyde into non-toxic acetic acid.
    • Many East Asians (e.g. about half of Japanese) have impaired acetaldehyde dehydrogenase.
    • Conversely, members of certain ethnicities who traditionally do not use alcoholic beverages have lower levels of alcohol dehydrogenases and thus "sober up" very slowly, but reach lower aldehyde concentrations and have milder hangovers.

  • Anaerobic Cellular Respiration

    • Some examples include alcohol fermentation in yeast and lactic acid fermentation in mammals.
    • The enzyme used in this reaction is lactate dehydrogenase (LDH).
    • Another familiar fermentation process is alcohol fermentation, which produces ethanol, an alcohol.
    • The use of alcohol fermentation can be traced back in history for thousands of years.
    • The second reaction is catalyzed by alcohol dehydrogenase to oxidize NADH to NAD+ and reduce acetaldehyde to ethanol.

  • Lipid Metabolism

    • Oxidation: The initial step of β-oxidation is catalyzed by acyl-CoA dehydrogenase, which oxidizes the fatty acyl-CoA molecule to yield enoyl-CoA.
    • Hydration: In the second step, enoyl-CoA hydratase hydrates the double bond introduced in the previous step, yielding an alcohol (-C-OH).
    • Oxidation: Hydroxyacyl-CoA dehydrogenase oxidizes the alcohol formed in the previous step to a carbonyl (-C=O).

  • Pyruvic Acid and Metabolism

    • Pyruvate from glycolysis is converted by fermentation to lactate using the enzyme lactate dehydrogenase and the coenzyme NADH in lactate fermentation.
    • Alternatively it is converted to acetaldehyde and then to ethanol in alcoholic fermentation.

  • Jaundice

    • Certain genetic diseases, such as sickle cell anemia, spherocytosis, thalassemia, and glucose 6-phosphate dehydrogenase deficiency can lead to increased red cell lysis and, therefore, hemolytic jaundice.
    • Hepatocellular (hepatic) jaundice can be caused by acute or chronic hepatitis, hepatotoxicity, cirrhosis, drug induced hepatitis, and alcoholic liver disease .

  • The Acetyl-CoA Pathway

    • The two major enzymes involved in these processes are carbon monoxide dehydrogenase and acetyl CoA synthase complex.
    • The carbon dioxide that is reduced to a carbonyl group, via the carbon monoxide dehydrogenase, is combined with the methyl group to form acetyl-CoA.
    • Carbon monoxide dehydrogenase, the enzyme responsible for the reduction of a carbon dioxide to a carbonyl group, functions in numerous biochemical processes.
    • The carbon monoxide dehydrogenase allows organisms to use carbon dioxide as a source of carbon and carbon monoxide as a source of energy.The carbon monoxide dehydrogenase can also form a complex with the acetyl-CoA synthase complex which is key in the acetyl-CoA pathway.
    • Describe the role of the carbon monoxide dehydrogenase and acetyl-CoA synthetase in the acetyl-CoA pathway

  • Control of Catabolic Pathways

    • If more energy is needed, more pyruvate will be converted into acetyl CoA through the action of pyruvate dehydrogenase.
    • Pyruvate dehydrogenase is also regulated by phosphorylation: a kinase phosphorylates it to form an inactive enzyme, and a phosphatase reactivates it.
    • These enzymes are isocitrate dehydrogenase and α-ketoglutarate dehydrogenase.
    • When more ATP is needed, as reflected in rising ADP levels, the rate increases. α-Ketoglutarate dehydrogenase will also be affected by the levels of succinyl CoA, a subsequent intermediate in the cycle, causing a decrease in activity.
    • Enzymes, isocitrate dehydrogenase and α-ketoglutarate dehydrogenase, catalyze the reactions that make the first two molecules of NADH in the citric acid cycle.

  • Organic Acid Metabolism

    • Methylotrophic microbes convert single-carbon compounds to formaldehyde, which is oxidized to formate by formaldehyde dehydrogenase.
    • Degradation of formate is then catalyzed by formate dehydrogenase (FDH), which oxidizes formate to ultimately yield CO2.
    • Fatty acid chains are converted to enoyl-CoA (catalyzed by acyl-CoA dehydrogenase).

  • Electron Donors and Acceptors

    • Electrons can enter the electron transport chain at three levels: dehydrogenase, the quinone pool, or a mobile cytochromeelectron carrier.
    • Note that electrons can enter the chain at three levels: at the level of a dehydrogenase , at the level of the quinone pool, or at the level of a mobile cytochrome electron carrier.
    • Bacteria can use a number of different electron donors, a number of different dehydrogenases, a number of different oxidases and reductases, and a number of different electron acceptors.
    • For example, E. coli (when growing aerobically using glucose as an energy source) uses two different NADH dehydrogenases and two different quinol oxidases, for a total of four different electron transport chains operating simultaneously.
    • Bacteria select their electron transport chains from a DNA library containing multiple possible dehydrogenases, terminal oxidases and terminal reductases.

  • Reactions of Alcohols

    • Alcohols can undergo elimination, but only by E1.
    • The acid protonates the alcohol to make it a good leaving group, then the halide displaces the alcohol with nucleophilic attack on the electrophilic carbon.
    • Although tertiary alcohols cannot be oxidized, secondary alcohols can be converted to ketones using an oxidizing agent.
    • On the left, a tertiary alcohol undergoes an SN1 reaction.
    • On the right, a primary alcohol undergoes an SN2 reaction.