Kinetic behaviour and degradative capability of Lentinula edodes laccase with differently substituted chlorinated substrates

Partially purified Lentinula edodes laccase was tested for its ability to oxidize several putative mono-, di- and tri-chlorinated substrates. Both the initial reaction rate and removal efficiency were remarkably affected by the nature of substituents and their position on the aromatic ring. Chlorinated phenols and/or anilines bearing an additional substituent with at least one lone pair electrons adjacent to the benzene ring were preferentially oxidized by the enzyme. In contrast, chlorinated substrates bearing an electron-withdrawing substituent, such as the nitro group, were not oxidized at all. The extent of removal of the most reactive chlorinated compounds after 1 h incubation with laccase was in the following order: chlorohydroquinone > 4,6-dichlororesorcinol > 2-amino-4-chlorophenol > 2,6-dichlorophenol > 2,4-dichlorophenol > 2,4,6-trichlorophenol > 2-chlorophenol > 4-chlorophenol.