Improved methods for the extraction of polyphenol oxidase from d'anjou pears

The conditions for extracting polyphenol oxidase (PPO, monophenol monooxygenase, EC 1.14.18.1) from d'Anjou pears have been studied. Water extracts of pear PPO contained artefacts which were present as additional bands on polyacrylamide-gel electrophoresis. Buffer extracts of an acetone powder did not remove sufficient endogenous phenolics to prevent browning of the extract. The following phenolic absorbents, arranged in order of increasing efficiency, reduced the formation of artefacts in extracts of PPO: PVPP, Amberlite XAD-4, Bio-Rad AG 1-X8, and Bio-Rad AG 2-X8. Greatest activity was extracted within a pH range of 5.6–5.9. Anion exchange resins were particularly effective in removing phenolics. XAD-4, AG 1-X8, or AG 2-X8 did not adsorb PPO and reduced the electrophoretically separable bands of PPO activity from 11 in water extracts to 3. The properties of the crude PPO were also studied.