title: Purification and thermal and high-pressure inactivation of pectinmethylesterase isoenzymes from tomatoes (Lycopersicon esculentum): a novel pressure labile isoenzyme.
abstract: Tomato pectinmethylesterase (PME) was successfully purified by a two-step method consisting of affinity chromatography followed by cation exchange chromatography. According to this procedure, four different isoenzymes were identified representing molar masses around 34.5-35.0 kDa. Thermal and high-pressure inactivation kinetics of the two major isoenzymes of tomato PME were studied. A striking difference between their process stability was found. The thermostable isoenzyme was completely inactivated after 5.0 min at 70 degrees C, whereas for the thermolabile isoenzyme, temperatures at around 60 degrees C were sufficient for complete inactivation. The thermostable isoenzyme was also found to be pressure stable since no inactivation was observed after 5.0 min of treatment at 800 MPa and 20 or 40 degrees C. The thermolabile isoenzyme appeared to be pressure labile since it could be completely inactivated after 5.0 min of treatment at 700 MPa and 20 degrees C or 650 MPa and 40 degrees C. Inactivation kinetics at pH 6.0 could be accurately described by a first-order model.
authors.affiliation: Center for Food and Microbial Technology, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium.
authors.forename: Lucía
authors.initials: L
authors.lastname: Plaza
authors.forename: Thomas
authors.initials: T
authors.lastname: Duvetter
authors.forename: Silvia
authors.initials: S
authors.lastname: Monfort
authors.forename: Elke
authors.initials: E
authors.lastname: Clynen
authors.forename: Liliane
authors.initials: L
authors.lastname: Schoofs
authors.forename: Ann M
authors.initials: AM
authors.lastname: Van Loey
authors.forename: Marc E
authors.initials: ME
authors.lastname: Hendrickx
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000302:isolation & purification* / Q000378:metabolism*; D004795:Enzyme Stability; D005638:Fruit / Q000201:enzymology*; D006358:Hot Temperature; D007527:Isoenzymes / Q000302:isolation & purification* / Q000378:metabolism*; D007700:Kinetics; D018551:Solanum lycopersicum / Q000201:enzymology*; D011312:Pressure
chemical_list: D007527:Isoenzymes; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase