Reduction of laccase type 1 copper by 3,4-dihydroxyphenylalanine and other catechol derivatives

Reactivity, electrochemical, and spectroscopic studies of type 2 copper-depleted Rhus vernicifera laccase

“…In spite of the similarity in rate constants, a significant difference should be noted in the rate laws for blue copper reduction in native and T2D laceases. Reactions of polyphenols with native lacease follow a two-step mechanism: rapid ES complex formation (formation constant Qp), followed by rate-limiting electron transfer to type 1 Cu(II) (rate constant k2) (Clemmer et al, 1979a;Wynn et al, 1983a). On this basis, eq 2 describes the relationship between kobid and *26p[H2Q-X]…”

“…i^^oposed functions of the type 2 copper atom in Rhus vernicifera lacease include the binding of polyphenolic substrates (Holwerda & Gray, 1974; Clemmer et al, 1979a), concerted two-electron reduction [type 1 and type 2 Cu(I)] of the binuclear type 3 copper center (Andréasson & Reinhammar, 1976, and a cooperative role, with the reduced type 3 site, in the rapid reduction of 02 to H20 (Branden & Deinum, 1977;Farver et al, 1980). Kinetic studies of the reduction of lacease by substituted hydroquinones (Clemmer et al, 1979a), 3,4-dihydroxy phenylalanine, and other catechol derivatives (Wynn et al, 1983a) have clarified the mechanism of electron transfer to the blue (type 1) copper atom and the mechanism of substrate binding in enzyme molecules with reduced type 3 sites. Coordination of singly ionized polyphenols to type 2 Cu(II) is thought to occur, with further stabilization of the enzyme-substrate complex arising from the interaction of lone-pair-bearing substituents on the aromatic ring with the type 3 cuprous atoms.…”

Ability of Various Chemicals to Reduce Copper and to Inactivate Mushroom Tyrosinase

“…Gallic acid was found to reduce type 1 copper of laccase (Wynn et al 1983). H,O, was also shown to be a reducing agent (Schoot Uiterkamp et al 1976).…”