Pectin methylesterases: cell wall enzymes with important roles in plant physiology.

Pectin methylesterases catalyse the demethylesterification of cell wall polygalacturonans. In dicot plants, these ubiquitous cell wall enzymes are involved in important developmental processes including cellular adhesion and stem elongation. Here, I highlight recent studies that challenge the accepted views of the mechanism and function of pectin methylesterases, including the co-secretion of pectins and pectin methylesterases into the apoplasm, new action patterns of mature pectin methylesterases and a possible function of the pro regions of pectin methylesterases as intramolecular chaperones.