Tyrosinase is a well-known copper-containing enzyme and is
widely distributed in microorganisms, plants and animals. In fungi and
vertebrates, tyrosinase catalyzes the rate-limiting step in the formation
of the pigment melanin from tyrosine. In plants, the physiological
substrates contain a variety of phenolics. Tyrosinase oxidizes them
in the browning pathway, observed when the plant tissues are
injured. The tyrosinase extracted from the champignon mushroom,
Agaricus bisporus, is highly homologous with the mammalian ones.
Hence, mushroom tyrosinase is well suited as a model for studies on
melanogenesis. Actually, almost all studies on tyrosinase inhibition
conducted so far have used mushroom tyrosinase, because only the
enzyme is commercially available. Tyrosinase has been ascribed
other functions apart from melanin production, including the
detoxification of host plant defensive phenols for symbiotic bacteria
[1,2], the sclerotisation of insect cuticles [3], and the synthesis of
amino acid based antibiotics [4]. Recently, the activities of tyrosinase
have been used in several biotechnological applications. Tyrosinase
has been applied in numerous of electrochemical biosensors, for a lot
of phenolic compounds. Also, tyrosinase has been applied to activate
the tyrosine residues in polypeptides for protein cross-linking to
chitosan films, as well as in direct protein-protein cross-linking.
Besides, tyrosinases could be applied to the removal of phenol from
wastewater and the bioconversion of L-tyrosine to L-DOPA [5].