Coordination environment and fluoride binding of type 2 copper in the blue copper protein ascorbate oxidase

J H Dawson; D M Dooley; H B Gray

doi:10.1073/pnas.77.9.5028

Coordination environment and fluoride binding of type 2 copper in the blue copper protein ascorbate oxidase

Proc Natl Acad Sci U S A. 1980 Sep;77(9):5028-31. doi: 10.1073/pnas.77.9.5028.

Authors

J H Dawson¹, D M Dooley, H B Gray

Affiliation

¹ Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125.

Abstract

The coordination environment of the type 2 (nonblue) copper in native ascorbate oxidase (L-ascorbate:oxygen oxidoreductase, EC 1.10.3.3) and of a derivative of the enzyme having the type 1 (blue) copper reversibly bleached has been examined by electron paramagnetic resonance (EPR) spectroscopy. In the g[unk] region of the spectrum of bleached ascorbate oxidase, a seven-line superhyperfine pattern is seen that is attributed to the presence of three nitrogen-donor ligands to a type 2 copper having tetragonal geometry. The superhyperfine splitting patterns in the g parallel region of the EPR spectra of native and bleached ascorbate oxidase show that as many as two fluorides may bind to type 2 copper. Because fluoride inhibits the enzyme competitively with respect to ascorbic acid, it is proposed that the type 2 copper is part of the ascorbate binding site.