Specific in hydrolyzing the terminal glycosidic bond of polygalacturonic acid and oligogalacturonates. Has no activity towards trigalacturonic acid. [(1->4)-alpha-D-galacturonosyl](n) + H2O = [(1->4)-alpha-D-galacturonosyl](n-1) + alpha-D-galacturonate Optimum pH is 4.0. Optimum temperature is 40 degrees Celsius. N-glycosylated. Belongs to the glycosyl hydrolase 28 family.