Oxyresveratrol is a stilbenoid described as a powerful inhibitor of tyrosinase and proposed as skin-whitening and anti-browning agent. However, the enzyme is capable of acting on it, considering it as a substrate, as it has been proved in the case of its analogous resveratrol. Tyrosinase hydroxylates the oxyresveratrol to an odiphenol and oxidizes the latter to an o-quinone, which finally isomerizes to p-quinone. For these reactions to take place the presence of the E ox (oxy-tyrosinase) form is necessary. The kinetic analysis of the proposed mechanism has allowed the kinetic characterization of this molecule as a substrate of tyrosinase, affording a catalytic constant of 5.

Peroxidase (PDD) and pectin methylesterase (PME) from tomato were characterized, studied thermal stability, and analyzed the synergistic effect of temperature and pH. For PDD, the optimal activity, using H 2 D 2 as substrate and ABTS +• as the donor H + , was obtained at pH 3.5, and for PME, the optimal activity using pectin as substrate was obtained at pH 7.5. On PDD, it was found that the values of K M , V m and K si for H 2 D 2 were 477.26 mM, 721.53 µM/min and 0.37 mM, respectively. On PME, the values of K M and V m obtained for pectin were 0.54 mM and 436.12 µM/min, respectively. Dn the other hand, it was found that PDD was inactivated with 90 °C, at pH from 2.5 to 3.5 with temperatures of 55 to 90 °C, and at pH of 2.5 to 3 with temperatures of 40 to 90 °C. Likewise, PME was inactivated at 90 °C, and at pH of 3.5 with 70 °C.