AN OPTICAL ROTATORY DISPERSION INVESTIGATION OF FUNGAL LACCASE

The optical rotatory dispersion curves for fungal laccase A and B have been determined in the wavelength region 200–750 nm. Both proteins show pronounced Cotton effects in the visible region. These are discussed in terms of possible chromophores (the so‐called Type 1 and Type 2 Cu2+ as well as the two diamagnetic copper ions). Various chemical treatments indicate that the anomalous dispersion is mainly associated with the blue, Type 1 Cu2+, which is thus coordinated in an asymmetric manner, but a small contribution from the Type 2 Cu2+ cannot be excluded. There are several Cotton effects in the ultraviolet region, probably associated with aromatic amino acids and peptide bonds in α‐helical configuration, but possible contributions from carbohydrates and disulfide bridges are also considered. The curves in the ultraviolet region do not change on complete reduction of the enzyme, indicating that there are no gross conformational changes on reduction and that the groups giving rise to the anomalous dispersion in this region are not associated with the electron‐accepting sites. Copyright © 1969, Wiley Blackwell. All rights reserved