Biochem/Physiol Actions | ADH (alcohol dehydrogenase) is one of the first enzymes to be isolated and purified. NAD+ is its coenzyme. Three isozymes of yeast ADH, that is, yeast alcohol dehydrogenase-1, 2 and 3 (YADH-1, -2, -3) have been identified. YADH-1 is expressed during anaerobic fermentation, YADH-2 is expressed in the cytoplasm and YADH-3 is localized to the mitochondria. A 141kDa tetramer containing 4 equal subunits. The active site of each subunit contains a zinc atom. Each active site also contains 2 reactive sulfhydryl groups and a histidine residue. Isoelectric point: 5.4-5.8 Optimal pH: 8.6-9.0 Substrates: Yeast ADH is most active with ethanol and its activity decreases as the size of the alcohol increases or decreases. Branched chain alcohols and secondary alcohols also have very low activity. KM (ethanol) = 2.1 × 10-2 M KM (methanol = 1.3 × 10-1 M KM (isopropanol) = 1.4 × 10-1 M Inhibitors: Compounds that react with free sulfhydryls, including N-alkylmaleimides and iodoacetamide. Zinc chelator inhibitors, including 1,10-phenanthroline, 8-hydroxyquinoline, 2,2′-dipyridyl, and thiourea. Substrate analogue inhibitors, including β-NAD analogs, purine and pyrimidine derivatives, chloroethanol, and fluoroethanol. Extinction Coefficient: E1% = 14.6 (water, 280 nm) |
