Phenolic acids affect transformations of chlorophenols by a Coriolus versicolor laccase

Partially-purified extracellular laccase of Coriolus versicolor transformed chlorophenols in the following order: 2,4,6-trichlorophenol>2,6-dichlorophenol>2,4-dichlorophenol, 2-chlorophenol>2,3-dichlorophenol. On the other hand, 3- and 4-chlorophenols, 2,5-, 3,4- and 3,5-dichlorophenols, 2,4,5-trichlorophenol and pentachlorophenol were recalcitrant to the laccase. Sinapinic acid, a naturally-occurring phenolic acid, enhanced transformations of 2,4,5- and 2,4,6-trichlorophenols, 2,4-dichlorophenol and 4-chlorophenol, whereas ferulic and p-coumaric acids inhibited transformations of 2,4,6-trichlorophenol, 2,3-, 2,4- and 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 first 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 first stage of the reaction but then its reaction intermediates irreversibly inactivated the laccase.