Polyphenoloxidases from Williams Pear (Pyrus communis L, cv Williams): Activation, Purification and Some Properties
✍ Scribed by Gauillard, Frédéric; Richard-Forget, Florence
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 252 KB
- Volume
- 74
- Category
- Article
- ISSN
- 0022-5142
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✦ Synopsis
Activation of a crude polyphenoloxidase (PPO) preparation extracted from Williams pears was investigated. Comparison between several activation agents led to the hypothesis of a limited conformational change involved in the activation process. Using ammonium sulphate precipitation followed by hydrophobic and ion exchange chromatography, two PPO fractions, F1 and F2, were 124-and 36-fold puriÐed. F1 contained two forms characterised by isoelectric point equal to 4É2 and 4É5 while F2 contained two other forms associated with isoelectric point of 3É8 and 4É0. The molecular mass determined by gel Ðltration and conÐrmed after SDS-page was unique (c 43 kDa). F1 and F2 showed similar apparent Km values, in the 5È11 mM range for the three main phenolic substrates in pear cortex. Chlorogenic acid appeared to be a better substrate than catechins for pear PPO.