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Different action patterns for apple pectin methylesterase at pH 7.0 and 4.5.
J M Denès1, A Baron, C M Renard
1Laboratoire de Recherches Cidricoles, Biotransformation des Fruits et Legumes, Institut National de la Recherche Agronomique, Le Rheu, France. abaron@rennes.inra.fr
Carbohydrate Research
|September 16, 2000
Summary
Apple pectin methylesterase (PME) acts on pectin using a multiple attack mechanism, with a high degree of multiple attack (≥10-11). This mechanism was observed at both optimal and apple juice pH conditions.
Area of Science:
- Biochemistry
- Enzymology
- Food Science
Background:
- Pectin methylesterase (PME) plays a crucial role in modifying pectin structure.
- Understanding PME's mechanism of action is vital for food processing and biotechnology.
Purpose of the Study:
- To elucidate the mechanism of action of purified apple pectin methylesterase (PME).
- To investigate PME's activity on pectin and homogalacturonans at different pH levels.
- To determine the interchain and intrachain distribution of de-esterified residues.
Main Methods:
- Enzymatic assays using pectin and methoxylated homogalacturonans.
- High-performance ion exchange chromatography (HPIEC) to analyze interchain distribution.
- Proton nuclear magnetic resonance (1H NMR) spectroscopy for intrachain analysis.
Main Results:
- Apple PME exhibited a multiple attack mechanism on pectic substrates.
- A high degree of multiple attack (≥10-11) was determined.
- Different interchain distributions of free carboxyl groups were observed at pH 7.0 and 4.5, while intrachain distributions remained similar.
Conclusions:
- Apple PME predominantly operates via a multiple attack mechanism.
- The enzyme's action pattern is influenced by pH, affecting interchain de-esterification.
- The findings provide insights into pectin modification by PME in apple-derived products.