EC - Tyrosinase

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IntEnz Enzyme Nomenclature


Accepted name:
Other names:
monophenol monooxygenase
monophenol oxidase
tyrosine-dopa oxidase
monophenol monooxidase
monophenol dihydroxyphenylalanine:oxygen oxidoreductase
N-acetyl-6-hydroxytryptophan oxidase
monophenol, dihydroxy-L-phenylalanine oxygen oxidoreductase
O-diphenol:O2 oxidoreductase
phenol oxidase
Systematic name:
L-tyrosine,L-dopa:oxygen oxidoreductase




A type III copper protein found in a broad variety of bacteria, fungi, plants, insects, crustaceans, and mammals, which is involved in the synthesis of betalains and melanin. The enzyme, which is activated upon binding molecular oxygen, can catalyse both a monophenolase reaction cycle (reaction 1) or a diphenolase reaction cycle (reaction 2). During the monophenolase cycle, one of the bound oxygen atoms is transferred to a monophenol (such as L-tyrosine), generating an O-diphenol intermediate, which is subsequently oxidized to an o-quinone and released, along with a water molecule. The enzyme remains in an inactive deoxy state, and is restored to the active oxy state by the binding of a new oxygen molecule. During the diphenolase cycle the enzyme binds an external diphenol molecule (such as L-dopa) and oxidizes it to an O-quinone that is released along with a water molecule, leaving the enzyme in the intermediate met state. The enzyme then binds a second diphenol molecule and repeats the process, ending in a deoxy state [7]. The second reaction is identical to that catalysed by the related enzyme catechol oxidase (EC However, the latter can not catalyse the hydroxylation or monooxygenation of monophenols.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Protein domains and families: PROSITE:PDOC00398
Structural data: CSA , EC2PDB
Gene Ontology: GO:0004503
CAS Registry Number: 9002-10-2
UniProtKB/Swiss-Prot: (36) [show] [UniProt]


  1. Dawson, C.R. and Tarpley, W.B.
    The copper oxidases.
    In: Sumner, J.B. and Myrbäck, K. (Eds.) The Enzymes, 1st ed. vol. 2, Academic Press, New York, 1951, 454-598
  2. Patil, S.S. and Zucker, M.
    Potato phenolases. Purification and properties.
    J. Biol. Chem. 240: 3938-3943 (1965). [PMID: 5842066]
  3. Pomerantz, S.H.
    Separation, purification, and properties of two tyrosinases from hamster melanoma.
    J. Biol. Chem. 238: 2351-2357 (1963).
  4. Robb, D.A.
    In: Lontie, R. (Ed.) Copper Proteins and Copper Enzymes vol. 2, C.R.C. Press, Boca Raton, FL, 1984, 207-240
  5. Sanchez-Ferrer, A., Rodriguez-Lopez, J. N., Garcia-Canovas, F., Garcia-Carmona, F.
    Tyrosinase: a comprehensive review of its mechanism.
    Biochim. Biophys. Acta 1247: 1-11 (1995). [PMID: 7873577]
  6. Steiner, U., Schliemann, W., Strack, D.
    Assay for tyrosine hydroxylation activity of tyrosinase from betalain-forming plants and cell cultures.
    Anal. Biochem. 238: 72-75 (1996). [PMID: 8660589]
  7. Rolff, M., Schottenheim, J., Decker, H., Tuczek, F.
    Copper-O2 reactivity of tyrosinase models towards external monophenolic substrates: molecular mechanism and comparison with the enzyme.
    Chem Soc Rev 40: 4077-4098 (2011). [PMID: 21416076]

[EC created 1972, modified 1976, modified 1980 (EC created 1972, incorporated 1984), modified 2012]