The ligninolytic enzyme system of Phanerochaete chrysosporium
decolorizes several recalcitrant dyes. Three isolated lignin peroxidase
isoenzymes (LiP 4.65, LiP 4.15, and LiP 3.85) were compared as
decolorizers with the crude enzyme system from the culture medium. LiP
4.65 (H2), LiP 4.15 (H7), and LiP 3.85 (H8) were purified by
chromatofocusing, and their kinetic parameters were found to be similar.
Ten different types of dyes, including azo, triphenyl methane,
heterocyclic, and polymeric dyes, were treated by the crude enzyme
preparation. Most of the dyes lost over 75% of their color; only Congo
red, Poly R-478, and Poly T-128 were decolorized less than the others,
54, 46, and 48%, respectively. Five different dyes were tested for
decolorization by the three purified isoenzymes. The ability of the
isoenzymes to decolorize the dyes in the presence of veratryl alcohol
was generally comparable to that of the crude enzyme preparation,
suggesting that lignin peroxidase plays a major role in the
decolorization and that manganese peroxidase is not required to start
the degradation of these dyes. In the absence of veratryl alcohol, the
decolorization activity of the isoenzymes was in most cases dramatically
reduced. However, LiP 3.85 was still able to decolorize 20% of
methylene blue and methyl orange and as much as 60% of toluidine blue O,
suggesting that at least some dyes can function as substrates for
isoenzyme LiP 3.85 but not to the same extent for LiP 4.15 or LiP 4.65.
Thus, the isoenzymes have different specificities towards dyes as
substrates.