Aromatic hydroxylation tyrosinase models

The xylyl hydroxylating system appears to possess a number of elements seen in enzyme catalyzed reactions, and the presence of a dicopper moiety, which effects a specific aromatic ring hydroxylation, identifies it as a tyrosinase model system. Analogous to the enzyme, either dieopper(I)/02 or met dicopper(II)/ H202 reactions result in xylyl hydroxylation. Although not yet proved absolutely, [Cu2(R—XYL—Y)(02)]2+ (11) is suggested to possess a p.-ii2 Ti2-022 structure, the one now favored for oxy-Hc and oxy-Tyr. Very likely, it acts as an electro-... 

The properties of Kitajima s p-p2 Ti2-pcroxo dicopper(II) complex lead to the conclusion that this is the likely structure in oxyhemocyanin and oxytyrosi-nase this is perhaps the most important contribution from this type of model chemistry. A distorted or closely related peroxo-dicopper(II) species appears to be involved in aromatic hydroxylation proceeding in a well-characterized tyrosinase model system. 

There has been extensive work aimed at elucidating the mechanism of aromatic hydroxylation. Most of that research was carried out with the aim of modeling tyrosinase, a copper-containing monooxygenase, and other aromatic systems of biological relevance. This subject is discussed in connection with the hydroxylation of phenols. 

Extensive work has been carried out by Karlin et al. on aromatic hydroxylation by tyrosinase models designed to mimic the coordination environment of copper in this enzyme. Copper(I) complexes of m-xylyl type dinucleating ligands bind 0 to form a p-peroxodicopper... 

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