Physical and enzymatic properties of a class II alcohol dehydrogenase isozyme of human liver: π-ADH

• Published in: Biochemistry (Easton) 1984-12, Vol.23 (26), p.6363-6368
• Main Authors: DITLOW, C. C, HOLMQUIST, B, MORELOCK, M. M, VALLEE, B. L
• Format: Article
• Language: English
• Subjects: Alcohol Dehydrogenase; Alcohol Oxidoreductases - antagonists & inhibitors; Alcohol Oxidoreductases - isolation & purification; Alcohol Oxidoreductases - metabolism; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Chelating Agents - pharmacology; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Humans; In Vitro Techniques; Isoenzymes - antagonists & inhibitors; Isoenzymes - isolation & purification; Isoenzymes - metabolism; Kinetics; Liver - enzymology; Oxidoreductases; Substrate Specificity
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00321a012

Homogeneous class II alcohol dehydrogenase (pi-ADH) has been isolated from human liver homogenates by chromatography on DE-52 cellulose, 4-[3-[N-(6-amino-caproyl)amino]propyl]pyrazole-Sepharose, SP-Sephadex C-50, and agarose-hexane-AMP, yielding an enzyme that has a significantly higher specific activity and is markedly more stable than that isolated by an earlier procedure. pi-ADH is composed of two identical 40 000-dalton subunits, contains 4 mol of zinc/dimer, and is readily inhibited by metal-chelating agents. The purified enzyme binds two molecules of coenzyme per dimer, exhibits an absorption maximum at 280 nm, epsilon 280 = 57 000, and exhibits an isoelectric point of 8.6. The class II isozyme catalyzes the oxidation of a variety of alcohols with Km values ranging from 7 microM to 560 mM and with kcat values from 32 min-1 to 600 min-1 and demonstrates a preference for hydrophobic substrates. The kcat/Km ratio for ethanol oxidation exhibits a pH maximum at 10.4.