Enzymatic activity of the A. bisporus tyrosinase in AOT/isooctane water-in-oil microemulsions

Agaricus bisporus tyrosinase was isolated and purified. Its activity in oxidation of 4-t-butylcatechol to 4-t-butyl-o-quinone was investigated in aqueous phosphate buffer solutions (pH 7.0), in the presence and absence of AOT (0–1.2 mM) as well as in AOT in isooctane w/o microemulsions, of variable AOT, water and substrate concentrations. In aqueous solutions AOT activated the enzyme at low concentrations and reduced its activity at higher ones (for about 20% of the initial reaction rate in 1 mM solutions). It reduced the initial rate of tyrosinase reactions in w/o microemulsions, too. The effects are discussed in terms of the substrate partitioning between the water pool, interfacial layer and isooctane phase, taking into account the fact that 4-t-butyl catechol behaves like a co-surfactant in the studied systems, and compared with the available literature data.