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 purified. F1 contained two forms characterised by isoelectric point equal to 4·2 and 4·5 while F2 contained two other forms associated with isoelectric point of 3·8 and 4·0. The molecular mass determined by gel filtration and confirmed after SDS-page was unique (c 43 kDa). F1 and F2 showed similar apparent Km values, in the 5–11 mM range for the three main phenolic substrates in pear cortex. Chlorogenic acid appeared to be a better substrate than catechins for pear PPO.
No takes yet. Share an insight, caveat, or question.
Gauillard et al. (1997) studied this question.