PartialPurificationAndCharacterizationOfPolyphenolOxidaseFromWild Pears (Pyrus communis)

ABSTRACT:precipitation,dialysisandionexchangechromatography.Ofthesubstratestested, pyrogallol wasthebettersubstrateforPPOwithaKm value of8.7mM at pH 5 and catechol is better with Km value 4.7 mM at pH 7.Theenzymeshowed high activity overabroad pHrange of4 – 8 so theoptimum pHforPPOactivity was foundtobe5 and 7. Theoptimal temperature forenzymeactivity wasfound tobe 45°C in presence of pyrogallol but 55°Cwith catechol as substrate at pH 7.Km value for wild pear PPO is calculated 9.5 and 4.7 mM for catechol and 8.7 and 5.1 mM for pyrogallol at pHs 5 and 7 respectively.Ascanbeseen,affinity ofPPOsforvarious substrates varies widely.Theenzymeshowedabroad activityoverabroadpHand temperaturerange. Thethermalinactivation studies showedthatthe enzyme isheat resistant.The enzymeshowed thehighest activity toward pyrogallol and noactivity towardtyrosine. Of the inhibitors tested, the mostpotent inhibitors was sodium kojic acid.