Protein LRET requires the existence of an amino acid
residue susceptible to form a stable radical (preferably a
tyrosine, tryptophan or histidine residue) located at the
protein surface and adequately connected to the haem
cofactor for electron transfer. The above authors suggested
two residues (Trp-171 and His-82) as the origin of
two LRET pathways for oxidation of high-redox-potential
aromatic compounds by LiP. Several years later a third
pathway was proposed (initiating at His-239) (Johjima
et al., 1999). No pathway starting at a tyrosine residue
has been proposed since all ligninolytic peroxidases
cloned up to date (a total of near 50 sequences) are free
of tyrosine residues (to prevent oxidative inactivation) with
the only exception of a Trametes cervina LiP discussed
below.