Acts in the modification of cell walls via demethylesterification of cell wall pectin (By similarity). Demethylates protein phosphatase 2A (PP2A) that have been reversibly carboxymethylated by LCMT1. Acts as negative regulators of genes involved in salt stress response (PubMed:28741704). [(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. Interacts with SBT6.1. Cleaved in the Golgi apparatus by SBT6.1 (S1P) after the Arg-Arg-Leu-Met (RRLM) and Arg-Arg-Leu-Leu (RRLL) motifs. This processing is required for extracellular targeting. Expressed in siliques. Expressed throughout silique development. The PMEI region may act as an autoinhibitory domain and prevent untimely PME activity during transport. The PMEI region is cleaved by SBT6.1 (S1P) in the Golgi apparatus prior to cell wall targeting. Reduced number of leaves at flowering time in long day conditions. In the N-terminal section; belongs to the PMEI family. In the C-terminal section; belongs to the pectinesterase family.