POLYOL DEHYDROGENASES OF AZOTOBACTER AGILIS

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Abstract
Marcus, Leon (University of California, Davis), and Allen G. Marr . Polyol dehydrogenases of Azotobacter agilis . J. Bacteriol. 82: 224–232. 1961.—Two soluble diphosphopyridine-linked polyol dehydrogenases are formed by Azotobacter agilis ( A. vinelandii ). The first, d -mannitol dehydrogenase is induced by d -mannitol and all of the pentitols except l -arabitol. Ribitol is an excellent inducer of mannitol dehydrogenase although it is not metabolized, nor does the enzyme act upon it. This allows study of the gratuitous induction of mannitol dehydrogenase. Of the polyols tested, mannitol dehydrogenase oxidizes d -mannitol, d -arabitol, d -rhamnitol, and perseitol, demonstrating its requirement for substrates bearing the d - manno configuration. The corresponding 2-ketoses, d -fructose, d -xylulose, and presumably d -rhamnulose, and perseulose are reduced. The second enzyme, l -iditol dehydrogenase is induced only by polyols containing the d - xylo configuration, i.e., sorbitol and xylitol. l -Iditol dehydrogenase oxidizes d - xylo polyols seven times faster than it does d - ribo polyols. Substrates oxidized include l -iditol, sorbitol, xylitol, and ribitol. The corresponding 2-ketoses, l -sorbose, d -fructose, d -xylulose, and d -ribulose, are reduced. The two polyol dehydrogenases have been separated and purified by chromatography on a modified cellulose ion exchanger.