The Dinuclear Copper Site Structure of Agaricus bisporus Tyrosinase in Solution Probed by X-ray Absorption Spectroscopy

Abstract

We have measured the x-ray absorption near edge structure (XANES) spectra of the enzyme tyrosinase from the mushroom Agaricus bisporus in solution in the oxy and deoxy forms. The spectra, obtained under the same conditions as the analogous forms of mollusc hemocyanin (Hc), show that the oxidation state of copper changes from Cu(II) (oxy form) to Cu(I) (deoxy form), and the copper active site(s) of A. bisporus tyrosinase in solution undergoes the same main conformational changes as Hc. We have applied the multiple scattering theory to simulate the XANES spectra of various alternative geometries of the copper site, accounting for the residual differences between Hc and tyrosinase. While oxy-Hc is reasonably fitted only by the pseudo-square-pyramidal geometry reported by its crystallographic data, oxytyrosinase can be fitted, starting from the Hc coordinates, either by distortions toward a pseudo-tetrahedral geometry, with inequivalent copper sites, or by an apically distorted square-pyramidal geometry (with an elongation of the apical distance of no more than 0.2 A).

Biochemical and spectroscopic characterization of catechol oxidase from sweet potatoes (Ipomoea batatas) containing a type‐3 dicopper center1

“…For the oxy form we considered the trend for an additional ligand as found by free refinement of the coordination numbers. Therefore five coordinated copper atoms are assumed in agreement with experiments on tyrosinase [42]. The resulting fits are in good agreement with the experimental data and are compared to these in Figs.…”

Melanogenesis, Tyrosinase Expression, and Reproductive Differentiation in Black and White Truffles (Ascomycotina)

“…known (Deinum et al, 1976;Robb, 1984;Sanchez-Ferrer et al, 1995;Della Longa et al, 1996); however the reversible inhibition of enzyme activity by BMTM and DMS, whose production is regulated during the life cycle of truffles, has not been described previously. In conclusion, as the ascocarp ripens, its flavour increases; animals that eat truffles are attracted to and eat them, thus spreading the spores, whose wall components are crosslinked (hardened) by quinones when tyrosinase is active.…”

Molecular Anatomy of Tyrosinase and its Related Proteins: Beyond the Histidine‐Bound Metal Catalytic Center

“…In this arrangement, the disposition of the coordination bond with the apical ligand is approximately perpendicular to the previous plane, and this could strongly affect the accessibility of the phenolic substrate to the active site. Analysis of XANES (X-ray absorption near edge structure) spectra indicated inequivalence of the two copper centers in Neurospora Tyr, whereas hemocyanins have a much higher structural order (34) at the active site.…”