Involved in the degradation of glucose and galactose via the Entner-Doudoroff pathway. Catalyzes the reversible cleavage of 2-keto-3-deoxy-6-phosphogluconate (KDPG) and 2-keto-3-deoxygluconate (KDG) forming pyruvate and glyceraldehyde 3-phosphate or glyceraldehyde, respectively. It is also able to catalyze the reversible cleavage of 2-keto-3-deoxy-6-phosphogalactonate (KDPGal) and 2-keto-3-deoxygalactonate (KDGal). 2-dehydro-3-deoxy-6-phospho-D-gluconate = D-glyceraldehyde 3-phosphate + pyruvate 2-dehydro-3-deoxy-6-phospho-D-galactonate = D-glyceraldehyde 3-phosphate + pyruvate Optimum pH is 5.5. Optimum temperature is around 90 degrees Celsius. Extremely thermostable. Carbohydrate acid metabolism; 2-dehydro-3-deoxy-D-gluconate degradation; D-glyceraldehyde 3-phosphate and pyruvate from 2-dehydro-3-deoxy-D-gluconate: step 2/2. Homotetramer; dimer of dimers. Belongs to the DapA family. KDPG aldolase subfamily.