Catalyzes the depolymerization of both polygalacturonate and pectins of various methyl esterification degree, with an endo mode of action. Shows the highest activity on 20 to 34% methylated pectin but retains 67%, 51%, 25%, and 1% of its maximum activity on polygalacturonate and 8.5%, 55 to 70%, and 90% methylated pectin, respectively. 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. Eliminative cleavage of (1->4)-alpha-D-galacturonan methyl ester to give oligosaccharides with 4-deoxy-6-O-methyl-alpha-D-galact-4-enuronosyl groups at their non-reducing ends. Optimum pH is 9.5. Optimum temperature is 40 degrees Celsius. Glycan metabolism; pectin degradation. Belongs to the polysaccharide lyase 1 family.