ABSTRACT

The Royal Sun mushroom, the Himematsutake culinary-medicinal mushroom, Agaricus brasiliensis has several polyphenoloxidase activities in a broad sense. Here we report the partial purification of tyrosinase-type polyphenoloxidase (PPO). PPO is purified from A. brasiliensis without browning using a two-phase partitioning with Triton X-114 and ammonium sulfate fractionation. Partially denaturing SDS-PAGE (sodium dodecyl sulfate-polyacrylamide electrophoresis) staining with L-3,4-dihydroxyphenylalanine was performed and the indicated molecular sizes were approximately 70 kDa and 45 kDa. The purified enzyme is in its latent state and can be activated maximally in the presence of 1.6 mM sodium dodecyl sulfate (SDS). This enzyme catalyzes two distinct reactions, monophenolase and diphenolase activity, and the monophenolase activity showed a lag time typical of polyphenoloxidase. The K_m value for 4-tert-butylcatechol was quite similar in the presence and absence of SDS, but the apparent V_max value was increased 2.0-fold by SDS. Mimosine was a typical competitive inhibitor with K_i values of 138.2 μM and 281.0 μM n the presence and absence of SDS, respectively.