The Effect of Fluoride on the Spectral and Catalytic Properties of Three Copper‐Containing Oxidases

Abstract

The optical spectra of fungal laccase, lacquer tree laccase and ceruloplasmin are changed in a similar way when F – is added to the proteins at pH 5.5. A change around 320 nm is associated with the binding of F – to type 2 Cu 2+ of the proteins as seen from a correlation with electron paramagnetic resonance spectra. The rate of binding of F – to fungal laccase is first order with respect to uncomplexed enzyme and independent of the F – concentration, indicating that an intramolecular process is rate limiting. The stability constant of the enzyme · F – complex is greater than 10 μM ‐1 . Fungal laccase is almost completely inhibited when 1 equivalent of F – is bound to the type 2 Cu 2+ . Presence of substrate gradually decreases the inhibition, due to the release of F – from a reduced form of the enzyme.