Protocatechuate 4,5-dioxygenase

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In enzymology, a protocatechuate 4,5-dioxygenase (EC is an enzyme that catalyzes the chemical reaction

protocatechuate + O2 4-carboxy-2-hydroxymuconate semialdehyde

Thus, the two substrates of this enzyme are protocatechuate and O2, whereas its product is 4-carboxy-2-hydroxymuconate semialdehyde.

This enzyme belongs to the family of oxidoreductases, specifically those acting on single donors with O2 as oxidant and incorporation of two atoms of oxygen into the substrate (oxygenases). The oxygen incorporated need not be derived from O2. The systematic name of this enzyme class is protocatechuate:oxygen 4,5-oxidoreductase (decyclizing). Other names in common use include protocatechuate 4,5-oxygenase, protocatechuic 4,5-dioxygenase, and protocatechuic 4,5-oxygenase. This enzyme participates in benzoate degradation via hydroxylation and 2,4-dichlorobenzoate degradation. It employs one cofactor, iron.

Structural studies

As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes 1B4U and 1BOU.


  • IUBMB entry for
  • BRENDA references for (Recommended.)
  • PubMed references for
  • PubMed Central references for
  • Google Scholar references for
  • Trippett S, Dagley S and Stopher DA (1960). "The bacterial oxidation of nicotinic acid". Biochem. J. 76: 9.

External links

The CAS registry number for this enzyme class is 9029-56-5.

Gene Ontology (GO) codes