Identification and characterization of d -arabinose reductase and d -arabinose transporters from Pichia stipitis.

d-xylose andl-arabinose are the major constituents of plant lignocelluloses, and the related fungal metabolic pathways have been extensively examined. AlthoughPichia stipitisCBS 6054 grows usingd-arabinose as the sole carbon source, the hypothetical pathway has not yet been clarified at the molecular level. We herein purified NAD(P)H-dependentd-arabinose reductase from cells grown ond-arabinose, and found that the enzyme was identical to the knownd-xylose reductase (XR). The enzyme activity of XR withd-arabinose was previously reported to be only 1% that withd-xylose. Thekcat/Kmvalue withd-arabinose (1.27 min−1 mM−1), which was determined using the recombinant enzyme, was 13.6- and 10.5-fold lower than those withl-arabinose andd-xylose, respectively. Among the 34 putative sugar transporters fromP. stipitis, only seven genes exhibited uptake ability not only ford-arabinose, but also ford-glucose and other pentose sugars includingd-xylose andl-arabinose inSaccharomyces cerevisiae. d-Xylose reductase, encoded byXYL1gene, plays as an aldose reductase involved not only ind-xylose andl-arabinose but alsod-arabinose metabolism. [ABSTRACT FROM PUBLISHER]