| Abstract
| - Tyrosinase oxidizes tyrosine to dopaquinone, which undergoesnonenzymatic reactions leading to precursors of melanin pigments.Cyclization of dopaquinone gives cyclodopa, which participates inredox exchange with dopaquinone to give the eumelanin precursordopachrome plus dopa. The indirect formation of the catechol(dopa) from the phenol (tyrosine) leads to unusual enzyme kinetics.Using a combination of enzyme oximetry, pulse radiolysis, andchemical oxidation, the study of structurally modified dopaquinones provides firm evidence of nonenzymatic catechol formationduring tyrosinase oxidation of phenols and reveals significantdifferences in their modes of reaction.
|
