Characterization of polyphenoloxidase activities from a wild and ediple mushroom Macrolepiota mastoidea

SUMMARY Characterization of Polyphenoloxidase Activities from a Wild and Edible Mushroom, Macrolepiota mastoidea In this study, a wild edible mushroom was evaluated for its polyphenoloxidase potentials. As a previous work, seven mushroom species were collected from the Lişer High Plateau-Maçka (Trabzon) and crude extracts were spectrophotometrically analyzed for either monophenolase or diphenolase activities. Of these mushroom species, Macrolepiota mastoidea as a wild edible mushroom species was determined to possess the greatest enzyme activities. Native electrophoresis stained by Z-dihydroxyphenylalanine of the crude extracts from this species showed two bands having Rf values of 0.38 (minor) and 0.47 (major) supporting a polyphenoloxidase potential. The crude extracts were able to possess both monophenolase activity against 3-(4-hydroxyphenyl)propionic acid (PHPPA) and diphenolase activity against 4-methylcatechol as substrates. Monophenolase and diphenolase activities of enzyme extract prepared from M. mastoidea showed pH optimum values at pH 6,0 for monophenolase and at pH 4,0 for diphenolase activities. When enzyme extracts were incubated at these pH values for 24 hours at 4 °C, it was observed that the extracts retained about 90% of their original monophenolase and diphenolase activities. It was estimated from thermodynamic data that monophenolase activity had higher thermal stability than that of diphenolase. Substrat saturation curves obtained for both enzymes in the presence of each individual substrate indicated that both enzymes followed simple Michaelis-Menten kinetics. Catalytic efficiencies for both enzyme activities were 15,2 dk"1 and 72,6 dk"1 for monophenolase and diphenolase, respectively. Some general polyphenoloxidase inhibitors inhibited both activities in the crude extracts. However, thiourea and ascorbic acid were highly potential inhibitor for monophenolase, and ascorbic acid and sodium metabisulphide for diphenolase activity. In addition, both enzyme activities were very sensitive to metal ions. It is clear from the present results, the enzyme extracts prepared from M. mastoidea possesses polyphenoloxidase activities with interesting properties. Key words: Polyphenoloxidase, Monophenolase, Diphenolase, M. mastoidea, Mushroom VI