Abstract

Polyphenol oxidase (PPO) from mushrooms (Agaricus bisporus (J.E.Lange) Imbach) was partially purified and characterized. The enzyme exhibited both monophenolase and diphenolase activities that were measured spectrophotometrically using L-tyrosine and pyrogallol as substrates. A two-fold purification in both activities was achieved by ammonium sulfate fractionation. The monophenolase activity was 3.35 EU/ml, and the diphenolase activity was 189.3 EU/ml. PPO was relatively stable at -15°C for 44 days. The enzyme was not very heat stable, and its activity decreased when incubated at the temperatures higher than 35°C. PPO activity showed two pH optima, at 5.3 and 7.0 at 25°C when pyrogallol was used as the substrate.

Mono-, di- and triphenols were substrates for PPO. Using Vmax/Km as a specificity constant, pyrocatechol was the better substrate followed by pyrogallol. The kinetic parameters of the enzyme were: Vmax = 78 EU/min/ml, Km = 1.4 mM and KS = 250 mM for pyrogallol and Vmax = 168 EU/min/ml, Km = 0.40 mM and KS = 270 mM for the pyrocatechol. Of the inhibitors tested, competitive-type inhibition was observed with benzoic acid and sodium azide. A mixed-type inhibition was observed with L-cysteine and sodium fluoride.

Recommended Citation

Gouzi, Hicham and Benmansour, Abdelhafid (2007) "Partial Purification and Characterization of Polyphenol Oxidase Extracted from Agaricus bisporus (J.E.Lange) Imbach," International Journal of Chemical Reactor Engineering: Vol. 5: A76.
Available at: http://www.bepress.com/ijcre/vol5/A76