Mode of de-esterification of alkaline and acidic pectin methyl esterases at different pH conditions |
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Authors: | Duvetter Thomas Fraeye Ilse Sila Daniel N Verlent Isabel Smout Chantal Hendrickx Marc Van Loey Ann |
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Affiliation: | Center for Food and Microbial Technology, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium. |
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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. |
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