Kinetics of activation of latent mushroom (Agaricus bisporus) tyrosinase by benzyl alcohol

A latent isoform of Agaricus bisporus tyrosinase has been isolated and acti vated by benzyl alcohol, one of the major volatile compounds in mushrooms o f this genus. The progress curve that describes the activation process reac hed the steady-state rate (V-ss) after a lag period (tau). The rate of acti ve tyrosinase formation was calculated by coupling the oxidation of o-diphe nols to the activation process. V-ss depended on benzyl alcohol, o-diphenol , and latent tyrosinase concentrations. The lag period depended on benzyl a lcohol concentrations but not on o-diphenol. and enzyme concentrations. The size of the latent mushroom tyrosinase was 67 kDa, determined by SDS-PAGE and Western blotting assays. This size was not modified after activation by benzyl alcohol. The presence of a lag period and the lack of change of the molecular mass of the protein after activation could indicate a slow confo rmational change of the protein tb render the final active form. The values of the kinetic constants V-max and K-m on the o-diphenols 4-tert-butylcate chol, L-DOPA, and dopamine were different between the latent tyrosinase act ivated by benzyl alcohol and the commercial tyrosinase. They might indicate that a different final active tyrosinase, depending on the activator used, could arise.