Alcohol is metabolized by all except

METABOLISM OF ALCOHOL -Alcohol absorption stas from the stomach itself, but most of it is absorbed by intestine. Only 1% of the ingested alcohol is excreted through the lungs or urine. Major fraction of the alcohol is oxidized in the liver. 1. Alcohol Dehydrogenase (ADH) - It is an NAD+ dependent cytoplasmic enzyme that oxidizes ethanol to acetaldehyde. Alcohol dehydrogenase is a dimer and has 6 isoenzymes. In some individuals the enzyme is mutated. This mutation rate is more in Orientals. In such individuals, alcohol metabolism is slower and even small quantity of alcohol may produce symptoms of intoxication. The enzyme was identified by Bateilli and Stern in 1909. 2. Aldehyde Dehydrogenase - Acetaldehyde is fuher oxidized to acetate by a mitochondrial NAD+ dependent enzyme. The acetate is then conveed to acetyl CoA. The activity of alcohol dehydrogenase is more than aldehyde dehydrogenase. So acetaldehyde accumulates in liver. Aldehyde is toxic, which in excess may lead to cell death. 3. Microsomal Ethanol Oxidizing System (MEOS) - It is another mechanism of detoxification of alcohol. It is cytochrome P450 dependent and is inducible. This accounts for metabolic tolerance of alcohol observed in chronic alcoholics. CH3-CH2-OH + NADPH + H+ + 2O2 --> CH3CHO + 2H2O2 + NADP+ REF: DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY,SIXTH EDITION,PG.NO.,121.