title: Mode of de-esterification of alkaline and acidic pectin methyl esterases at different pH conditions.
abstract: Highly esterified citrus pectin was de-esterified at pH 4.5 and 8.0 by a fungal pectin methyl esterase (PME) that was shown to have an acidic isoelectric pH (pI) and an acidic pH optimum and by a plant PME that was characterized by an alkaline pI and an alkaline pH optimum. Interchain and intrachain de-esterification patterns were studied by digestion of the pectin products with endo-polygalacturonase and subsequent analysis using size exclusion and anion-exchange chromatography. No effect of pH was observed on the de-esterification mode of either of the two enzymes. Acidic, fungal PME converted pectin according to a multiple-chain mechanism, with a limited degree of multiple attack at the intrachain level, both at pH 4.5 and at pH 8.0. A multiple-attack mechanism, with a high degree of multiple attack, was more appropriate to describe the action mode of alkaline, plant PME, both at pH 4.5 and at pH 8.0.
authors.affiliation: Center for Food and Microbial Technology, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium.
authors.forename: Thomas
authors.initials: T
authors.lastname: Duvetter
authors.forename: Ilse
authors.initials: I
authors.lastname: Fraeye
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Sila
authors.forename: Isabel
authors.initials: I
authors.lastname: Verlent
authors.forename: Chantal
authors.initials: C
authors.lastname: Smout
authors.forename: Marc
authors.initials: M
authors.lastname: Hendrickx
authors.forename: Ann
authors.initials: A
authors.lastname: Van Loey
mesh_terms: D001230:Aspergillus / Q000201:enzymology; D002265:Carboxylic Ester Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D002957:Citrus / Q000737:chemistry; D004951:Esterification; D006863:Hydrogen-Ion Concentration; D018551:Solanum lycopersicum / Q000201:enzymology; D010368:Pectins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D010368:Pectins; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase