Temperature dependence of the reduction potential of blue copper in fungal laccase

Creators: Taniguchi, Vernon T.; Malmström, Bo G.; Anson, Fred C.; Gray, Harry B.

Abstract

Thin-layer spectroelectrochemical methods have been employed to measure the reduction potentials of the blue copper in Polypors veruicolor laccase (EC 1.10.3.2) between 7°C and 41°C (0.2 M sodium phosphate, pH 5.4). Thermodynamic parameters are: ΔS° = -13.9 ± 2 cal/mol-K; ΔH° = -22.1 ± 0.5 kcal/mol; E° (25°C) = 780 ± 3 mV vs. the normal hydrogen electrode. Comparison of the ΔS° and ΔH° values with those for single-site proteins suggests that the high potential of the blue copper in fungal laccase is attributable mainly to stabilization of the copper (I) center by enhanced ligand binding interactions and that protein solvation effects play a lesser role.

Additional Information

© 1982 by the National Academy of Sciences. Contributed by Harry B. Gray, February 22, 1982. We thank Grant Mauk for providing a sample of potassium octacyanomolybdate(IV) dihydrate and Ann-Cathrine Carlsson for preparing the fungal laccase. This research was supported by National Institutes of Health Grant AM19038 and the Swedish Natural Science Research Council. B.G.M. was a Sherman Fairchild Distinguished Scholar at the California Institute of Technology during 1980-1981. This is contribution no. 6607 from the Arthur Amos Noyes Laboratory. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.

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