Monophenolase activity of latent Terfezia claveryi tyrosinase:: Characterization and histochemical localization

The monophenolase activity of Terfezia claveryi tyrosinase (EC 1.14.18.1) is described for the first time. This enzyme is fully latent and can only be detected if SDS is present in the reaction medium. Monophenolase activity was localized within the ascocarp using histochemical techniques. A detailed kinetic study of the parameters affecting this activity has been carried out. Both the characteristic lag period and the steady-state rate are affected by pH and the enzyme and substrate concentrations. The presence of catalytic concentrations of o-diphenols affected the lag period but not the steady-state rate. By increasing the concentration of o-diphenols, it was possible to evaluate the enzyme activation constant, K-act, which showed a value of 7.2 muM. The experimental results are compatible with the mechanism previously described for tyrosinases from other sources.