NADP-dependent D-xylose dehydrogenase involved in the degradation of D-xylose, a major component of hemicelluloses such as xylan. Even if it shows D-xylose dehydrogenase activity, it is not essential for D-xylose degradation. D-xylose + NADP(+) = D-xylono-1,5-lactone + H(+) + NADPH Homotetramer. Expression is highly induced during growth on D-xylose. Does not affect growth on D-xylose as sole energy and carbon substrate. Belongs to the Gfo/Idh/MocA family.