(582db) The Uptake of Cu in Tyrosinase Affects the Monophenolase/Diphenolase Activity Ratio

Tyrosinase belongs to the type-3 copper enzyme family, containing a di-nuclear Cu center, CuA and CuB. It is mainly responsible for melanin production in a wide range of organisms. Although Cu ions are essential for the activity of tyrosinase, the mechanism of Cu uptake is still unclear. We have recently determined the crystal structure of tyrosinase from Bacillus megaterium (TyrBm) and revealed that this enzyme has tighter binding of CuA in comparison to CuB. Investigating Cu accumulation in TyrBm, it was found that Cu presence has a more significant effect on the diphenolase activity. Therefore, by decreasing the concentration of Cu, the diphenolase/molophenolase ratio was increased by 2-fold. Using a rational design approach, we identified five variants having an impact on Cu uptake. We have found that a major role of the highly conserved Asn205 residue is to stabilize the orientation of the His204 imidazole ring in the binding site, thereby promoting the correct coordination of CuB. Further investigation of these variants revealed that Phe197, Met61 and Met184, which are located at the entrance to the binding site, not only play a role in Cu uptake but are also important for enhancing the diphenolase activity. In this study we propose a mechanism of Cu accumulation as well as an approach to changing the selectivity of TyrBm towards L-dopa production.