NADP-dependent D-xylose dehydrogenase involved in the degradation of D-xylose, a major component of hemicelluloses such as xylan. Catalyzes the initial reaction in the xylose utilization pathway by oxydizing D-xylose into D-xylonolactone. D-xylofuranose + NADP(+) = D-xylono-1,4-lactone + H(+) + NADPH Homotetramer. Transcriptionally up-regulated by both L-arabinose and D-xylose via the pentose-specific regulator XacR. Impairs growth on D-xylose as sole energy and carbon substrate. Belongs to the Gfo/Idh/MocA family.