Pectinesterases (PEs; pectin pectyl-hydrolase, EC
3.1.1.11) have been found in all species of higher plants
(Deuel & Stutz, 1958; Lineweaver & Jansen, 1951) and
are also produced by certain plant pathogenic fungi and
bacteria (Fogarty & Kelly, 1983). The enzymes catalyze
the de-esterification of pectin and convert protopectin
to soluble pectin and pectate. The decrease in degree of
esterification (DE) is relevant to the fruit maturation
process.