Physical and enzymic properties of a class II alcohol dehydrogenase isozyme of human liver: .pi.-ADH

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Abstract
Homogeneous class II alcohol dehydrogenase (.pi.-ADH) was isolated from human liver homogenates by chromatography on DE-52 cellulose, 4-[3-[N-(6-aminocaproyl)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 2 identical 40,000-dalton subunits, contains 4 mol of Zn/dimer, and is readily inhibited by metal-chelating agents. The purified enzyme binds 2 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 .mu.M 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.
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