Hydrogen peroxide producing enzymes such as glyoxal oxidase, and
laccase (copper-containing polyphenol oxidase) are also
considered important in the process of lignin bio-degradation
(Cullen & Kersten, 1996). Laccase may also act as a scavenger
system by promoting polymerization of toxic compounds
produced by lignin degrading enzymes (Thurston, 1994).
Laccase protein from A. bisporus which is expressed constitutively
at high levels during vegetative growth (Wood,
1980), was purified (Perry et al., 1993a) and two laccase
encoding genes were cloned (Perry et al., 1993b). Comparison
of these laccase genes with other fungal laccases and
functionally related ascorbate oxidases from plants showed
that, whilst regions around the amino acids that are involved
in copper binding are absolutely conserved, the overall
sequence similarities are low