Identification of a radical intermediate in the enzymatic reduction of oxygen by a small laccase.
The enzyme mechanism of the Cu-containing small laccase (SLAC) from Streptomyces coelicolor has been investigated by optical and electron paramagnetic resonance spectroscopy. A new intermediate was identified after the reaction of molecular oxygen with the reduced trinuclear site of the type-1-depleted (T1D) form of the enzyme. It has the fingerprint of a biradical with a triplet ground state. One of the spins resides on a Cu in the trinuclear site, tentatively identified as the type-2 site, while the other spin derives from a protein-based radical. The latter is tentatively identified as a tyrosyl radical on the basis of the similarity of the optical characteristics with those observed for a Cu tyrosyl radical pair. The spin-spin distance was found to be 5.0 +/- 0.2 A.
Tepper
Armand W J W
AW
Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands.
Milikisyants
Sergey
S
Sottini
Silvia
S
Vijgenboom
Erik
E
Groenen
Edgar J J
EJ
Canters
Gerard W
GW
D000042:Absorption; D020134:Catalytic Domain; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000032:analysis / Q000378:metabolism; D042845:Laccase / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D020037:Sordariales / Q000201:enzymology; D013057:Spectrum Analysis
D005609:Free Radicals; D042845:Laccase; D010100:Oxygen