Enzymatic Basis for d-Arabitol Production by Saccharomyces rouxii1

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Ingram, Jordan M. (Michigan State University, East Lansing), and W. A. Wood. Enzymatic basis for d-arabitol production by Saccharomyces rouxii. J. Bacteriol. 89:1186–1194. 1965.—The enzymatic steps in d-arabitol synthesis by Saccharomyces rouxii were studied. The fermentation of d-glucose-6-C14 gave rise to d-arabitol labeled at C-5; d-ribose of ribonucleic acid had the same isotope pattern. Crude extracts were able to reduce d-ribulose with reduced nicotinamide adenine dinucleotide phosphate (NADPH2) and d-xylulose with reduced nicotinamide adenine dinucleotide (NADH2). These extracts also oxidized d-arabitol with nicotinamide adenine dinucleotide phosphate and xylitol with nicotinamide adenine dinucleotide. No reduction of d-ribulose-5-phosphate or d-xylulose-5-phosphate was observed. An enzyme which reduced d-xylulose with NADH2 was purified 33-fold and characterized as a xylitol (→ d-xylulose) dehydrogenase. Similarly, an enzyme reducing d-ribulose with NADPH2 was purified 12-fold and characterized as a d-arabitol (→ d-ribulose) dehydrogenase. Alkaline and acid phosphatases were purified 50- and 40-fold, respectively, and their specificities were determined. Only the acid phosphatase had detectable activity on d-ribulose-5-phosphate. The data support the postulate that d-arabitol arises by dephosphorylation of d-ribulose-5-phosphate and reduction of d-ribulose by a NADPH2-linked d-arabitol (→ d-ribulose) dehydrogenase.

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