A resonance Raman investigation of perturbed states of tree and fungal laccase

DF Blair, GW Campbell, V Lum, CT Martin, HB Gray, BG Malmström, Sunney I. Chan, Journal of Inorganic Biochemistry 19, 65-73

Resonance Raman (RR) spectra of Rhus vernicifera laccase and Polyporus versicolor laccase in several perturbed states are reported. Coordination of fluoride to the type 2 copper of either laccase does not produce RR-detectable changes at the type 1 sites. Removal of the type 2 copper of Rhus laccase induces RR-detectable changes at the type 1 site that are most readily interpreted as arising from a heterogeneous sample. Freezing the Rhus laccase does not induce changes in its RR spectrum; further cooling to liquid nitrogen temperature induces a change in the type 1 site that is reflected in the RR spectrum. Electron paramagnetic resonance spectra confirm that the structure of the type 1 site is temperature dependent. Some variability in the Rhus laccase RR spectrum is observed in the absence of exogenous ligands or other perturbations; it is suggested that Rhus laccase preparations may be heterogeneous with respect to the structure of the type 1 copper site.