Monkey Liver Indanol Dehydrogenase. Purification, Properties, and Kinetic Mechanism1

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Abstract
Indanol dehydrogenase was purified to apparent homogeneity from monkey liver cytosol. The enzyme was a monomer with a molecular weight of 36, 000 and pi of 8.7. The amino acid composition was determined. The enzyme oxidized alicyclic alcohols including trans-dihydrodiols of benzene and naphthalene in the presence of both NADP+ and NAD+ and reduced several xenobiotic carbonyl compounds in the presence of NADPH, the 4-pro-R hydrogen atom of which was transferred to the substrate. The results of fluorometric binding and kinetic studies are consistent with an ordered sequential mechanism with NADP+ binding first. The enzyme was inhibited competitively versus NADP+ and un-competitively versus 1-indanol not only by cheiating agents such as 1, 10-phenanthroline and 2, 2 -bipyridine but also by a nonchelating isomer, 4, 4'-bipyridine, which suggests hydrophobic interaction of the aromatic compounds with the enzyme, which did not contain zinc. The enzyme was also inhibited by Cibacron blue dye, synthetic estrogens, and δ4–3-ketosteroids. The inhibition by Cibacron blue was competitive versus NADP+ and noncompetitive versus 1-indanol, whereas those by hexestrol, medroxyprogesterone acetate, and progesterone were uncompetitive versus NADP+ and competitive versus 1-indanol, corraborating the ordered addition of the coenzyme prior to 1-indanol.

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