Enkephalins and exorphins oxidation by tyrosinase.

Tyrosinase activity was tested on some tyrosine-containing peptides (enkephalins and exorphins). All they are substrates for tyrosinase, showing a good affinity for the enzyme, in some cases higher than tyrosine itself. Aminoacid analysis after hydrolysis of long-lasting incubation mixtures of tyrosinase with Leu-enkephalin in presence of reductants demonstrates the formation of DOPA. The production of a new peptide containing DOPA derived from the oxidation of Leu-enkephalin was revealed by high performance liquid chromatography (HPLC).