May function in depolymerizing pectin during pollen development, germination, and tube growth. Acts as an exo-polygalacturonase. [(1->4)-alpha-D-galacturonosyl](n) + H2O = [(1->4)-alpha-D-galacturonosyl](n-1) + alpha-D-galacturonate Causes an allergic reaction in human. Binds to IgE. Induces basophil activation from blood of S.kali pollen-sensitized patients. Belongs to the glycosyl hydrolase 28 family.