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Effect of pH on the oxidation pathway of alpha-methyldopa catalysed by tyrosinase
P Serna Rodríguez1, J N Rodríguez López, J Tudela
1Departamento de Bioquímica y Biología Molecular, Facultad de Biología, Universidad de Murcia, Spain.
Abstract:
This paper deals with the quantitative description of the effect of pH on the oxidation pathway of alpha-methyldopa. Tyrosinase catalyses the oxidation by molecular oxygen of alpha-methyldopa to o-alpha-methyldopaquinone, which evolves non-enzymically through a branched pathway with cyclization or hydroxylation reactions. The intermediates of the hydroxylation branch have been identified, and the corresponding rate constants have been determined. These compounds, which have been detected in melanosomes and in tumour cells, have great cytotoxic power and could have physiological significance in acidic media.