ISOLATION AND SOME PROPERTIES OF AN ACIDIC FRACTION OF POLYPHENOL OXIDASE FROM JERUSALEM ARTICHOKE(HELIANTHUS TUBEROSUS L.)

Some Kinetic Properties of Polyphenol Oxidase Obtained from Various Salvia Species (Salvia Viridis L., Salvia Virgata Jacq. and Salvia Tomentosa Miller)

Polyphenol oxidase (PPO) was partially purified by (NH4)2SO4 precipitation followed by dialysis from different organs of Salvia species (Salvia virgata Jacq., Salvia viridis L. and Salvia tomentosa Miller). Polyphenol oxidase activity was measured spectrophotometrically at 420 nm using catechol as a substrate. Vmax, KM and Vmax/KM values for polyphenol oxidase activity from different organs of Salvia species were determined. S. tomentosa Miller was the species with the highest PPO activity, followed by S. virgata Jacq and S. viridis L. S. tomentosa Miller was the most suitable Salvia species for dark-tea preparations because of the highest Vmax/KM values. The effects of various inhibitors on the reaction catalysed by the enzyme were tested and calculated I50 values, reduced the enzyme activity by 50%. The most effective inhibitor was L-cysteine followed by ascorbic acid. Activation energies, Ea, were determined from Arrhenius equation.