2,5-dioxopentanoate dehydrogenase involved in the degradation of pentoses such as D-arabinose or D-xylose, a major component of hemicelluloses such as xylan. Catalyzes the fifth reaction in the pentose utilization pathway through dehydratation of 2,5-dioxopentanoate into 2-oxoglutarate. Shows also dehydrogenase activity toward glycolaldehyde and DL-glyceraldehyde. 2,5-dioxopentanoate + H2O + NADP(+) = 2-oxoglutarate + 2 H(+) + NADPH Optimum pH is 7.8. Homotetramer. Expression is highly induced during growth on D-arabinose. The promoter contains the conserved cis-regulatory element 5'-AACATGTT-3' ARA-box found in arabinose-induced genes. Belongs to the aldehyde dehydrogenase family.