Active Oxygen Species Involved in the Dye-Sensitized Photoinactivation of Mushroom Tyrosinase

Active oxygen species were responsible for affecting the inactivation of native mushroom tyrosinase at pH 7.0 in photodynamic systems containing rose bengal and riboflavin. The effects of scavengers, quenchers, and D₂O indicated that H₂O₂and O₂-were the primary active oxygen species generated by the riboflavin-sensitized reaction, and ¹O₂was the primary species generated by the system containing rose bengal. Diazabicyclo[2.2.2]octane (DABCO), Hepes, and Mops accelerated tyrosinase inactivation, and this was attributed to their ability to form secondary radical adducts or generate free radicals in the presence of copper. The effects of $$OH scavengers and the chelators, EDTA, phytate, and desferrioxamine mesylate (DFOM), indicated that (1) bulk-phase metal-driven Fenton reactions were not responsible for tyrosinase photoinactivation and (2) site-specific generation of $$OH from a copper-driven Fenton reaction played a role in enzyme inactivation.