Purification and Properties of Xylitol Dehydrogenase from the Xylose-fermenting Yeast Candida shehatae

Xylitol dehydrogenase (EC1.1.1.9) from xylose-grown cells of Candida shehatae was purified 215-fold by sequential chromatography on NADC8 affinity, Superose-12, and Cibacron blue columns, and a single band was observed by SDS gel electrophoresis. The purified enzyme had a native molecular weight of 82 kDa and a denatured molecular weight of 40 kDa following SDS gel electrophoresis, indicating that it was composed of two subunits. Alcohol dehydrogenase copurified on the NAD-C8 but was substantially removed by Superose-12 and was not detected following Cibacron blue chromatography. The kinetic properties of the C. shehatae xylitol dehydrogenase differed consider­ ably from those described previously for the Pachysolen tannophilus enzyme. The Km of the C. shehatae enzyme for xylitol was 3.8 times smaller, whereas the Km for xylulose was 1.7-fold bigger. These fac­ tors could account for the lower xylitol production by C. shehatae. Index Entries: Candida shehatae; xylitol dehydrogenase; xylose metabolism; pentose pathway; xylose fermentation. *Author to whom all correspondence and reprint requests should be addressed. Applied Biochemistry and Biotechnology Editor-in-Chief: H. Weetall 1990 The Humana Press Inc.