Cleaves unsaturated oligo-galacturonides from pectin. The major product is trigalacturonate; digalacturonate and tetragalacturonate are also produced. Activity on methylated pectins decreases with an increasing degree of methylation (By similarity). eliminative cleavage of unsaturated trigalacturonate as the major product from the reducing end of polygalacturonic acid/pectate. Belongs to the polysaccharide lyase 1 family.