INHIBITION OF MUSHROOM POLYPHENOL OXIDASE BY AGARITINE

Agaritine mma-L(+)-glutamyl)-4-hydroxymethylphenylhydrazine] was isola ted and purified from mushrooms (Agaricus bisporus). This paper report s for the first time the inhibition of the monophenolase and diphenola se activities of mushroom polyphenol oxidase by this abundant and char acteristic compound from the Agaricus genus. Agaritine showed uncompet itive inhibition (K-I = 2.3 mM) and partial competitive inhibition (K- I = 0.13 mM; alpha = 2.5) when L-DOPA and L-tyrosine were assayed, res pectively. In addition to the ability of agaritine to inhibit the enzy me per se, this compound was capable of removing the enzymatically gen erated o-quinones in the assay. To solve this problem, the inhibition was characterized by using 3-methyl-2-benzothiazolinone hydrazone as n ucleophile reagent to form a stable nucleophile-quinone adduct that co uld not be attacked by agaritine. The inhibition of mushroom polypheno l oxidase by other inhibitors is compared to the inhibition by agariti ne. Moreover, a possible role for agaritine in the browning of mushroo ms is discussed.