Significant Enhancement of Monooxygenase Activity of Oxygen Carrier Protein Hemocyanin by Urea

Oxygenation of a series of p-substituted phenols to the corresponding catechols (phenolase activity) by the (μ-η²:η²-peroxo)dicopper(II) species of Octopus hemocyanin has been directly examined for the first time by using a UV−vis spectroscopic method in a 0.5 M borate buffer solution containing 8 M urea under anaerobic conditions. Preliminary kinetic studies have indicated that the reaction involves an electrophilic aromatic substitution mechanism as in the case of phenolase reaction of tyrosinase. The oxygenation of phenols by hemocyanin also proceeded catalytically when the reaction was carried out under aerobic conditions.