Purification and properties of polyphenol oxidase from mango peel (Mangifera indica var. Raspuri).

Polyphenol oxidase from the peel of ripe mango fruit was purified 126-fold to homogeneity by (NH4)2SO4 fractionation, column chromatography on Blue Sepharose CL-6B and gel chromatography on Sephadex G-200. It had an iso-electric point (pI) of 4.1plus/minus0.2 and mol. wt. of 137 000 daltons as determined by sodium dodecyl sulphate - polyacrylamide gel electrophoresis and gel filtration. It was more specific for catechol (than for other substrates tested) with a Km of 8.2mM . 2-Mercaptoethanol, L -cysteine, sodium diethyldithiocarbamate and thiourea were effective inhibitors of this enzyme. It had pH and temp. optima of 5.5 and 46 degree C, resp. It lost 50% activity by exposure to 85 degree , 75 degree and 65 degree C for 3, 16 and 25.5 min, resp. Copper content was 1 atom/mole of enzyme and copper was essential for its activity. Unlike most of the polyphenol oxidases, multiple forms were not detected in the crude extract.