InterPro: IPR018040 Pectinesterase, active site

Pectinesterase EC:3.1.1.11 (pectin methylesterase) catalyses the de-esterification of pectin into pectate and methanol. Pectin is one of the main components of the plant cell wall. In plants, pectinesterase plays an important role in cell wall metabolism during fruit ripening. In plant bacterial pathogens such as Erwinia carotovora and in fungal pathogens such as Aspergillus niger, pectinesterase is involved in maceration and soft-rotting of plant tissue. Plant pectinesterases are regulated by pectinesterase inhibitors, which are ineffective against microbial enzymes [1].

Prokaryotic and eukaryotic pectinesterases share a few regions of sequence similarity. The crystal structure of pectinesterase from Erwinia chrysanthemi revealed a beta-helix structure similar to that found in pectinolytic enzymes, though it is different from most structures of esterases [2]. The putative catalytic residues are in a similar location to those of the active site and substrate-binding cleft of pectate lyase.

This entry represents conserved sequence regions found in these proteins, one of which (Pectinesterase signature 2) contains the active site aspartate [3].