Catechol oxidase

 

Catechol oxidase is a type 3 copper protein that exclusively catalyses the oxidation of catechols (e.g. o-diphenols) to the corresponding o-quinones. The enzyme can also act on a variety of substituted catechols. Although a member of the same superfamily as tyrosinase, it is a different enzyme.

 

Reference Protein and Structure

Sequence
Q9ZP19 UniProt (1.10.3.1) IPR002227 (Sequence Homologues) (PDB Homologues)
Biological species
Ipomoea batatas (Sweet potato) Uniprot
PDB
1bt3 - CATECHOL OXIDASE FROM IPOMOEA BATATAS (SWEET POTATOES) IN THE NATIVE CU(II)-CU(II) STATE (2.5 Å) PDBe PDBsum 1bt3
Catalytic CATH Domains
1.10.1280.10 CATHdb (see all for 1bt3)
Cofactors
Cu-o-cu linkage (1) Metal MACiE
Click To Show Structure

Enzyme Reaction (EC:1.10.3.1)

dioxygen
CHEBI:15379ChEBI
+
catechol
CHEBI:18135ChEBI
→
water
CHEBI:15377ChEBI
+
1,2-benzoquinone
CHEBI:17253ChEBI
Alternative enzyme names: o-diphenol oxidoreductase, o-diphenol:oxygen oxidoreductase, o-diphenolase, Dopa oxidase, Catecholase, Diphenol oxidase, Phenolase, Polyphenol oxidase, Pyrocatechol oxidase, Tyrosinase,

Enzyme Mechanism

Introduction

There is little or no direct involvement of amino acid residues in the proposed mechanism. A hydroxide ion (activated water) bridges the two copper centres. This activates the diphenol, resulting in an electron transfer from one of the copper centres to the dioxygen molecule. The dioxygen radical abstracts a hydrogen from the other hydroxyl group on the Cu-bound intermediate. The phenolic racidal then donates a second electron to the copper centre. The anionic oxygen of the peroxide group deprotonates the second molecule of benzene-1,2-diol, which causes a hydride to be eliminated from the second phenol group, and cleaved of the peroxo bond. The second Cu(I) centre donates a single electron to the second phenol group. The anionic oxygen of the peroxide group deprotonates the second molecule of benzene-1,2-diol, which causes a hydride to be eliminated from the second phenol group, and cleaved of the peroxo bond. The second Cu(I) centre donates a single electron to the second phenol group.

Catalytic Residues Roles

UniProt PDB* (1bt3)
His274, His244, His240 His274A, His244A, His240A Forms the Copper B binding site. metal ligand
Phe261 Phe261A Phe261 blocks access of the ortho protons of the phenolic ring thus limiting the enzyme to oxygenase activity and not hydroxylase activity. steric role, polar/non-polar interaction
His118, His88, His109 His118A, His88A, His109A Forms the Copper A binding site. metal ligand
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

proton transfer, bimolecular nucleophilic substitution, redox reaction, bimolecular homolytic addition, radical formation, overall reactant used, coordination to a metal ion, cofactor used, decoordination from a metal ion, intermediate formation, overall product formed, hydrogen transfer, radical propagation, electron transfer, radical termination, elimination (not covered by the Ingold mechanisms), intermediate terminated, native state of cofactor regenerated, hydride transfer, intermediate collapse, native state of enzyme regenerated

References

  1. Siegbahn PE (2004), J Biol Inorg Chem, 9, 577-590. The catalytic cycle of catechol oxidase. DOI:10.1007/s00775-004-0551-2. PMID:15185133.
  2. Güell M et al. (2007), J Biol Inorg Chem, 12, 1251-1264. Theoretical study of the catalytic mechanism of catechol oxidase. DOI:10.1007/s00775-007-0293-z. PMID:17891425.
  3. Tepper AW et al. (2005), J Am Chem Soc, 127, 567-575. Interaction between the Type-3 Copper Protein Tyrosinase and the Substrate Analoguep-Nitrophenol Studied by NMR. DOI:10.1021/ja0454687. PMID:15643881.
  4. Olivares C et al. (2002), Biochemistry, 41, 679-686. Identification of Active Site Residues Involved in Metal Cofactor Binding and Stereospecific Substrate Recognition in Mammalian Tyrosinase. Implications to the Catalytic Cycle†. DOI:10.1021/bi011535n.
  5. Klabunde T et al. (1998), Nat Struct Biol, 5, 1084-1090. Crystal structure of a plant catechol oxidase containing a dicopper center. DOI:10.1038/4193. PMID:9846879.

Step 1. The bridging hydroxide deprotonates the benzene-1,2-diol, which initiates a nucleophilic attack on the Cu(I) centre, initiating a single electron transfer to dioxygen. The dioxygen radical then replaces the water as the bridging ligand between the two copper centres.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
His88A metal ligand
His109A metal ligand
His118A metal ligand
His240A metal ligand
His244A metal ligand
His274A metal ligand
Phe261A polar/non-polar interaction, steric role

Chemical Components

proton transfer, ingold: bimolecular nucleophilic substitution, redox reaction, ingold: bimolecular homolytic addition, radical formation, overall reactant used, coordination to a metal ion, cofactor used, decoordination from a metal ion, intermediate formation, overall product formed

Step 2. The dioxygen radical abstracts a hydrogen from the other hydroxyl group on the Cu-bound intermediate.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
His88A metal ligand
His109A metal ligand
His118A metal ligand
His240A metal ligand
His244A metal ligand
His274A metal ligand
Phe261A polar/non-polar interaction, steric role

Chemical Components

hydrogen transfer, radical propagation, intermediate formation

Step 3. The oxyanion collapses, initiating double bond rearrangement that forms 1,2-benzoquinone and causes a single electron to be transferred to the Cu(II) centre.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
His88A metal ligand
His109A metal ligand
His118A metal ligand
His240A metal ligand
His244A metal ligand
His274A metal ligand
Phe261A polar/non-polar interaction, steric role

Chemical Components

electron transfer, radical termination, elimination (not covered by the Ingold mechanisms), decoordination from a metal ion, intermediate terminated, native state of cofactor regenerated, overall product formed

Step 4. The anionic oxygen of the peroxide group deprotonates the second molecule of benzene-1,2-diol, which causes a hydride to be eliminated from the second phenol group, and cleaved of the peroxo bond. The second Cu(I) centre donates a single electron to the second phenol group.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
His88A metal ligand
His109A metal ligand
His118A metal ligand
His240A metal ligand
His244A metal ligand
His274A metal ligand
Phe261A polar/non-polar interaction, steric role

Chemical Components

proton transfer, redox reaction, hydride transfer, ingold: bimolecular nucleophilic substitution, radical formation, overall reactant used, cofactor used, intermediate collapse, overall product formed

Step 5. The phenolate undergoes double bond rearrangement that causes a single electron to be donated back to the Cu(II) centre, and formation of 1,2-benzoquinone.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
His88A metal ligand
His109A metal ligand
His118A metal ligand
His240A metal ligand
His244A metal ligand
His274A metal ligand
Phe261A polar/non-polar interaction, steric role

Chemical Components

electron transfer, radical termination, native state of cofactor regenerated, intermediate terminated, overall product formed, native state of enzyme regenerated
Download: Image, Marvin File

Step 1. The bridging hydroxide deprotonates the benzene-1,2-diol, which initiates a nucleophilic attack on the Cu(I) centre, initiating a single electron transfer to dioxygen. The dioxygen radical then replaces the water as the bridging ligand between the two copper centres.

Step 2. The dioxygen radical abstracts a hydrogen from the other hydroxyl group on the Cu-bound intermediate.

Step 3. The oxyanion collapses, initiating double bond rearrangement that forms 1,2-benzoquinone and causes a single electron to be transferred to the Cu(II) centre.

Step 4. The anionic oxygen of the peroxide group deprotonates the second molecule of benzene-1,2-diol, which causes a hydride to be eliminated from the second phenol group, and cleaved of the peroxo bond. The second Cu(I) centre donates a single electron to the second phenol group.

Step 5. The phenolate undergoes double bond rearrangement that causes a single electron to be donated back to the Cu(II) centre, and formation of 1,2-benzoquinone.

Products.

Contributors

Gemma L. Holliday, Daniel E. Almonacid, Atlanta Cook, Craig Porter