Tyrosinase reactivity in a model complex: an alternative hydroxylation mechanism.
The binuclear copper enzyme tyrosinase activates O2 to form a mu-eta2:eta2-peroxodicopper(II) complex, which oxidizes phenols to catechols. Here, a synthetic mu-eta2:eta2-peroxodicopper(II) complex, with an absorption spectrum similar to that of the enzymatic active oxidant, is reported to rapidly hydroxylate phenolates at -80 degrees C. Upon phenolate addition at extreme temperature in solution (-120 degrees C), a reactive intermediate consistent with a bis-mu-oxodicopper(III)-phenolate complex, with the O-O bond fully cleaved, is observed experimentally. The subsequent hydroxylation step has the hallmarks of an electrophilic aromatic substitution mechanism, similar to tyrosinase. Overall, the evidence for sequential O-O bond cleavage and C-O bond formation in this synthetic complex suggests an alternative intimate mechanism to the concerted or late stage O-O bond scission generally accepted for the phenol hydroxylation reaction performed by tyrosinase.
Mirica
Liviu M
LM
Department of Chemistry, Stanford University, CA 94305, USA.
Vance
Michael
M
Rudd
Deanne Jackson
DJ
Hedman
Britt
B
Hodgson
Keith O
KO
Solomon
Edward I
EI
Stack
T Daniel P
TD
D001665:Binding Sites; D002384:Catalysis; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003080:Cold Temperature; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D006900:Hydroxylation; D008024:Ligands; D008956:Models, Chemical; D014442:Monophenol Monooxygenase / Q000737:chemistry / Q000378:metabolism*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D010636:Phenols / Q000737:chemistry* / Q000378:metabolism
D008024:Ligands; D009942:Organometallic Compounds; D010636:Phenols; C501836:bis-mu-oxodicopper(III)-phenolate complex; D003300:Copper; D014442:Monophenol Monooxygenase; D010100:Oxygen