Apr 23, 1999

Targeted mutations in a Trametes villosa laccase. Axial perturbations of the T1 copper

The Journal of Biological Chemistry
F XuEdward I Solomon

Abstract

Trametes villosa laccase was mutated on a tetrapeptide segment near the type 1 site. The mutations F463M and F463L were at the position corresponding to the type 1 copper axial methionine (M517) ligand in Zucchini ascorbate oxidase. The mutations E460S and A461E were near the T1 copper site. The mutated Trametes laccases were expressed in an Aspergillus oryzae host and characterized. The E460S mutation failed to produce a transformant with meaningful expression. The F463L and A461E mutations did not significantly alter the molecular and enzymological properties of the laccase. In contrast, the F463M mutation resulted in a type 1 copper site with an EPR signal intermediate between that of the wild type laccase and plastocyanin, an altered UV-visible spectrum, and a decreased redox potential (by 0.1 V). In oxidizing phenolic substrate, the mutation led to a more basic optimal pH as well as an increase in kcat and Km. These effects are attributed to a significant perturbation of the T1 copper center caused by the coordination of the axial methionine (M463) ligand.

  • References11
  • Citations55

References

  • References11
  • Citations55

Citations

Mentioned in this Paper

Mutagenesis, Site-Directed
Aspergillus flavus var. oryzae
Oxidase
Plastocyanin Activity
L-Ascorbate oxidase
Laccase B
Trametes
Etiology
Copper
Substrate Specificity

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