01641naa a2200193 a 450000100080000000500110000800800410001902200140006010000200007424500900009426000090018452011100019365000100130365000160131365300130132970000180134270000180136077300690137816326462023-05-02       1993    bl uuuu     u00u1 u    #d  a0310-78411 aROBINSON, S. P.  aPolyphenol oxidase enzymes in the sap and skin of mango fruit.h[electronic resource]  c1993  aSevere occurs in mango fruit of the cultivar Kensington when sap contacts the fruit, resulting in browning and then blackening of the skin. Both the sap and skin of mango fruit contained considerable polyphenol oxidase (PPO) activity. The sap enzyme was not activated by SDS, was inhibited by hexadecyltrimethylammonium bromide, and was active with both para-and ortho-diphenol substrates. The skin enzyme was activated by SDS, was inhibited by salicylhydroxamic acid and polyvinylpyrrolidone, and active only with ortho-diphenol substrates. These properties suggest that the sap PPO is a laccase-type enzyme (EC 1.10.3.2) whereas the skin contains the common catwchol oxidase-type PPO (EC 1.10.3.1). The skin enzyme had a temperature optimum at 30 degrees C but the enzyme had maximum PPO activity at 75 degrees C. Both enzymes were relatively thermostable, requiring more than 15 min at 80 degrees C for 50% loss of activity. It is concluded that browning of mango skin induced by the sap is predominantly catalysed by PPO in the skin and this is unlikely to be prevented by heat treatment of the fruit.  aFungo  aTemperatura  aCultivar1 aLOVEYS, B. R.1 aCHACKO, E. K.  tAustralian Journal of Plant Physiologygv.20, n.1, p.99-107,1993