Catalyzes the dehydration of L-2-keto-3-deoxyarabonate (L-KDA) to alpha-ketoglutaric semialdehyde (alphaKGSA). Is involved in a degradation pathway of L-arabinose that allows A.brasilense to grow on L-arabinose as a sole carbon source. 2-dehydro-3-deoxy-L-arabinonate = 2,5-dioxopentanoate + H2O Homodimer. Belongs to the DapA family.