NADP-dependent D-xylose dehydrogenase catalyzing the oxydation of D-xylose into D-xylonolactone. Also displays some, albeit lower activity with D-glucose, D-galactose and L-arabinose as substrate. Probably not involved in D-xylose degradation, as it has been shown that H.jecorina assimilates D-xylose via D-xylose reductase and xylitol dehydrogenase, and it is unable to grow on D-xylonic acid as sole carbon source. May play a role in the regeneration of NADP(+) in the presence of D-xylose. D-xylose + NADP(+) = D-xylono-1,5-lactone + H(+) + NADPH Belongs to the Gfo/Idh/MocA family.