MetaCyc Enzyme: hydroquinone 1,2-dioxygenase

Species: Pseudomonas fluorescens ACB

Subunit composition of hydroquinone 1,2-dioxygenase = [HapD]2[HapC]2
         hydroquinone dioxygenase large subunit = HapD
         hydroquinone dioxygenase small subunit = HapC

This enzyme is an extradiol-type dioxygenase that catalyzes the conversion of benzene-1,4-diol to (2E,4Z)-4-hydroxy-6-oxohexa-2,4-dienoate. It is a novel member of the nonheme-iron(II)-dependent dioxygenase family. It did not show any significant amino acid sequence identity with known dioxygenases [Moonen08].

The native apparent molecular mass of this α2β2 heterotetrameric enzyme was determined by online size-exclusion chromatography/mass spectrometry to be 112.4 kDa, composed of an α subunit of 17.8 kDa and a β subunit of 38.3 kDa. The β subunit contains binding sites for Fe2+ and the competitive inhibitor 4-hydroxybenzoate. The spectral properties of the enzyme also suggested an extradiol-type dioxygenase [Moonen08a].

Molecular Weight: 112.4 kD (experimental) [Moonen08a ]

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

Created 29-Feb-2012 by Fulcher CA , SRI International

Enzymatic reaction of: hydroquinone 1,2-dioxygenase

Synonyms: hydroquinone 1.2-dioxygenase

EC Number:

benzene-1,4-diol + oxygen <=> (2E,4Z)-4-hydroxy-6-oxohexa-2,4-dienoate + H+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: 4-hydroxyacetophenone degradation

The enzyme catalyzed the ring cleavage of a wide range of hydroquinone substrates to produce the corresponding 4-hydroxymuconic semialdehydes. Use of the competitive inhibitor 4-hydroxybenzoate during purification prevented irreversible inactivation of the enzyme [Moonen08a].

The Km value was determined at pH 7.0, 25 °C. A variety of phenolic compounds inhibited the enzxyme [Moonen08a].

Activators (Unknown Mechanism): Fe2+ [Moonen08a]

Inhibitors (Competitive): 4-hydroxybenzoate (Kic = 14µM) [Moonen08a]

Inhibitors (Unknown Mechanism): 2,2'-dipyridyl [Moonen08a] , o-phenanthroline [Moonen08a] , hydrogen peroxide [Moonen08a]

Kinetic Parameters:

Km (μM)

pH(opt): 7-8 [Moonen08a]

Subunit of hydroquinone 1,2-dioxygenase: hydroquinone dioxygenase large subunit

Synonyms: HapD, hydroquinone dioxygenase β subunit

Gene: hapD Accession Number: G-14992 (MetaCyc)

Molecular Weight: 38.403 kD (from nucleotide sequence)

Unification Links: UniProt:B1GRL9

Relationship Links: InterPro:IN-FAMILY:IPR011051 , InterPro:IN-FAMILY:IPR014710

Subunit of hydroquinone 1,2-dioxygenase: hydroquinone dioxygenase small subunit

Synonyms: hydroquinone dioxygenase α subunit

Gene: HapC Accession Number: G-14991 (MetaCyc)

Molecular Weight: 17.841 kD (from nucleotide sequence)

Unification Links: UniProt:B1GRL8

Relationship Links: InterPro:IN-FAMILY:IPR011051 , InterPro:IN-FAMILY:IPR014710


Moonen08: Moonen MJ, Kamerbeek NM, Westphal AH, Boeren SA, Janssen DB, Fraaije MW, van Berkel WJ (2008). "Elucidation of the 4-hydroxyacetophenone catabolic pathway in Pseudomonas fluorescens ACB." J Bacteriol 190(15);5190-8. PMID: 18502868

Moonen08a: Moonen MJ, Synowsky SA, van den Berg WA, Westphal AH, Heck AJ, van den Heuvel RH, Fraaije MW, van Berkel WJ (2008). "Hydroquinone dioxygenase from pseudomonas fluorescens ACB: a novel member of the family of nonheme-iron(II)-dependent dioxygenases." J Bacteriol 190(15);5199-209. PMID: 18502867

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 19.0 on Wed Oct 7, 2015, biocyc14.