Catalysis of the reaction: a pectin = an oligosaccharide with 4-deoxy-6-O-methyl-alpha-D-galact-4-enuronate end + a pectin. This reaction is the 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 nonreducing ends.