An Optical Rotatory Dispersion Investigation of Fungal Laccase

Abstract

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.

Optical properties of japanese-lacquer-tree (Rhus vernicifera) laccase depleted of type 2 copper(II). Involvement of type-2 copper(II) in the 330nm chromophore

“…Discussion C.d. measurements showed that the Type 2 Cu(II) of lacquer-tree laccase does not significantly contribute to the optical activity of the protein in the 400-650nm region, in agreement with previous data concerning this and other multicopper blue proteins (Bossa et al, 1969;Falk & Reinhammar, 1972). On the other hand, it certainly contributes to the absorbance above 650nm; the A614/A750 ratio increased from about 4.6 in the native protein to about 6.5 in the partial apoprotein.…”

Chemical Relaxation Study of the Electron Transfer Between Laccase and External Redox Couples

“…Experiments were carried out on the T-jump spectropolarimeter with the laccase-Mo(CN)f/3-system at the optically active 610 nm band [25] . No separate chemical relaxation could be resolved from that due to transmission change occurring upon reduction of the 610 nm band.…”

Environment of copper in Pseudomonas fluorescens Azurin: fluorometric approach

“…Conversely the lowering of the dielectric constant of the environment, produced by the addition of sodium dodecyl sulfate in acidic solution (Konev, 1967) brings back the emission maximum to 310 nm (Figure 3). In this context it should be recalled that acidic pH {i.e., pH 1.5) leads to the disappearance (Tang and Coleman, 1967;Tang et al, 1968) of the multiple Cotton effects which are present in azurin and laccase at neutral pH (Tang and Coleman, 1967;Tang et al, 1968;Bossa et al, 1969) in the region of aromatic amino acids (270-300 nm). This indicates that dissymmetry and hydrophobic character are strictly associated in the tryptophan-containing part of the protein.…”

“…The absorption spectra of most "blue" proteins show the characteristic ripples on the aromatic peak. Some of them have been found to have abnormal Cotton effects in the aromatic region (Tang and Coleman, 1967;Tang et al, 1968;Bossa et al, 1969).…”