Catalyzes the reversible retro-aldol cleavage of both 5-keto-4-deoxy-D-glucarate and 2-keto-3-deoxy-D-glucarate to pyruvate and tartronic semialdehyde. 5-dehydro-4-deoxy-D-glucarate = 2-hydroxy-3-oxopropanoate + pyruvate 2-dehydro-3-deoxy-D-glucarate = 2-hydroxy-3-oxopropanoate + pyruvate Binds 1 Mg(2+) ion per subunit. Can also use, although less efficiently, Co(2+), Fe(2+) and Mn(2+). Inhibited by acetate, chloride and bromide ions, nitrate, fluoride, cyanide, EDTA and pyrophosphate. Optimum pH is 7.4-8.6. Stable from pH 6 to 7.5. Carbohydrate acid metabolism; galactarate degradation; D-glycerate from galactarate: step 2/3. Homohexamer; trimer of dimers. Induced by D-galactarate, D-glucarate and D-glycerate. The catalytic mechanism was originally thought to use a phosphate as the catalytic acid, but this was subsequently disputed (PubMed:15996099, PubMed:17881002 and PubMed:18754683). Belongs to the HpcH/HpaI aldolase family. KDGluc aldolase subfamily. Was wrongly named 2-dehydro-3-deoxygalactarate aldolase (DDG aldolase or DDGA) in PubMed:10921867. 2-dehydro-3-deoxygalactarate is the enantiomer of 5-dehydro-4-deoxy-D-glucarate, but is not an isomer obtained in the degradation pathway of D-glucarate/galactarate and the enzyme has not been shown to be active on it.