Acts in the modification of cell walls via demethylesterification of cell wall pectin. Plays an important role in growth of pollen tubes in female floral tissues, possibly via enhancing the interaction between the pollen tube and female floral tissues by modification of the cell walls. [(1->4)-alpha-D-galacturonosyl methyl ester](n) + n H2O = [(1->4)-alpha-D-galacturonosyl](n) + n H(+) + n methanol Glycan metabolism; pectin degradation; 2-dehydro-3-deoxy-D-gluconate from pectin: step 1/5. Expressed in pollen grains and pollen tubes. The PMEI region may act as an autoinhibitory domain and prevent untimely PME activity during transport. In the N-terminal section; belongs to the PMEI family. In the C-terminal section; belongs to the pectinesterase family. Probable cloning artifact leading to a large internal deletion.