Phenolic acids aect transformations of chlorophenols by a Coriolus versicolor laccase

Partially-puri®ed extracellular laccase of Coriolus versicolor transformed chlorophenols in the following order: 2,4,6trichlorophenol > 2,6-dichlorophenol > 2,4-dichlorophenol, 2-chlorophenol > 2,3-dichlorophenol. On the other hand, 3and 4chlorophenols, 2,5-, 3,4and 3,5-dichlorophenols, 2,4,5-trichlorophenol and pentachlorophenol were recalcitrant to the laccase. Sinapinic acid, a naturally-occurring phenolic acid, enhanced transformations of 2,4,5and 2,4,6-trichlorophenols, 2,4dichlorophenol and 4-chlorophenol, whereas ferulic and p-coumaric acids inhibited transformations of 2,4,6-trichlorophenol, 2,3-, 2,4and 2,6-dichlorophenols and 2-chlorophenol. The three phenolic acids have similar chemical structures. Further examination using sinapinic and ferulic acids and 2,4-dichlorophenol revealed that sinapinic acid competitively inhibited the transformation of 2,4-dichlorophenol at the ®rst stage of the reaction, but its reaction intermediates likely enhanced the transformation of 2,4-dichlorophenol. Ferulic acid also competitively inhibited the transformation of 2,4-dichlorophenol at the ®rst stage of the reaction but then its reaction intermediates irreversibly inactivated the laccase. # 2000 Elsevier Science Ltd. All rights reserved.