Eliminative cleavage of (1->4)-alpha-D-galacturonan to give oligosaccharides with 4-deoxy-alpha-D-galact-4-enuronosyl groups at their non-reducing ends. Binds 1 Ca(2+) ion. Required for its activity. Glycan metabolism; pectin degradation; 2-dehydro-3-deoxy-D-gluconate from pectin: step 2/5. Belongs to the polysaccharide lyase 1 family. It is uncertain whether Met-1 or Met-2 is the initiator.