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Xylose reductase (alditol: NADP^+ 1-oxidoreductase, EC 1.1.1.21) from the xylosefermenting yeast, Candida sp. BT001, was purified via salt fractionation, ion-exchange, gel filtration and affinity chromatography, and its properties were characterized. The enzyme from the yeast was active with both NADPH and NADH as coenzyme. The xylose reductase activity with NADH was approximately 51% of that with NADPH and the specific activities of purified enzyme with NADPH and NADH were 11.78 U/㎎ and 6.01 U/㎎, respectively. Molecular weight of the purified enzyme was 31,000 on SDS-PAGE and 61,000 on gel filtration. The Km for D-xylose, NADPH, and NADH was 94.2×10^(-3)M, 0.011×10^(-3)M, and 0.032×10^(-3)M, respectively. The purified xylose reductase had relatively higher substrate affinity for L-arabinose than other aldoses tested. The optimal pH was 6.2 and the optimal reaction temperature was 45℃. The thermal stability of the enzyme was for 20 minutes at 30℃.
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