Acts in the modification of cell walls via demethylesterification of cell wall pectin. Inhibits the elongation phase of protein synthesis. [(1->4)-alpha-D-galacturonosyl methyl ester](n) + n H2O = [(1->4)-alpha-D-galacturonosyl](n) + n H(+) + n methanol Endohydrolysis of the N-glycosidic bond at one specific adenosine on the 28S rRNA. Glycan metabolism; pectin degradation; 2-dehydro-3-deoxy-D-gluconate from pectin: step 1/5. Expressed in siliques, flowers, floral stems, rosette leaves and roots. Expressed during early seed development and late developmental phases of siliques. 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.