Direct observation by EPR of a reductively decoupled type 3 site in type 2 copper depleted laccase.

New epr features consistent with a novel type of Cu(II) are observed in partially reduced Type 2 copper depleted laccase molecules. Cu(II) hyperfine lines appear near 2590 G and 2770 G, and a rhombic g1 feature is also observed. These reflect a Cu(II) emergent on reductive disruption of the binuclear Type 3 site in T2D laccase. Additionally, much of the new, magnetically isolated Cu(II) is retained on full reoxidation of partly reduced Type 2 copper depleted laccase. The proportion of disrupted Type 3 Cu(II) sites remaining after reoxidation appears to depend on the prior distribution of electrons within T2D laccase.