Catalyzes the dehydration of galactarate to form 5-dehydro-4-deoxy-D-glucarate (5-KDG). galactarate = 5-dehydro-4-deoxy-D-glucarate + H2O kcat is 22 sec(-1). Carbohydrate acid metabolism; galactarate degradation; D-glycerate from galactarate: step 1/3. Homodimer. Induced by galactarate, D-glucarate and D-glycerate. Consists of three domains. The N-terminal SAF domain, which forms a beta-clip fold, is likely involved in the substrate recognition. It is connected by a long unstructured linker to the second domain, which serves as a dimerization interface between two monomers. The C-terminal domain represents the catalytic core of the protein and probably contains the metal binding site. Belongs to the UxaA family.