| Root |
Created: 8 May 1997
| Mononuclear iron centre | Iron ligands | Formal iron oxidation/spin states |
|---|---|---|
 His)2(O Tyr)2OH |
His;
2 × O OH¯ |
FeIII (S = 5/2) |
His)2OTyr-Substrate |
His;
O
|
FeII (S = 2);
FeIII (S = 5/2) |
The aromaticringcleavage dioxygenases open the aromatic ring by incorporating two atoms of dioxygen (O2) in their substrates, typically carrying two or more hydroxyl groups on the aromatic ring [1, 2]. If two of the hydroxyl groups of a substrate are in the ortho position, the ring fission by the intradiol aromaticringcleavage dioxygenases (IARCD) occurs between the two hydroxyl groups (1) (cf. extradiol aromaticringcleavage dioxygenases):
 |
 |
 |
(1) |
ß)n
or homodimers
()n.
3,4PCD contain equal numbers of
and ß subunits and form
different quaternary structures of
(ß)n
(n = 3 to 12) [1].
The sequence similarity between 1,2CTD and the
and ß subunits of 3,4PCD
suggests common ancestry of IARCD [3].
The bestcharacterised IARCD, 3,4PCD, catalyses the cleavage of an
aromatic ring of 3,4dixydroxybenzoate to form a dicarboxylic acid
(2).
Each of the carboxylate groups contains one of the oxygen atoms from
O2 [4].
The 3D structure of 3,4PCD from Pseudomonas aeruginosa has
been determined [5].
The enzyme exists as a highly symmetric
(
A substrate activation mechanism for IARCD has been proposed
[2, 4,
6].
(2)
ß)12 aggregate.
The and ß subunits
share the same fold; the core comprises a sandwich composed of seven
ßstrands (see Figure 2PCD a).
The active site of the enzyme lies at the interface between the
and ß subunits,
although all the iron ligands are provided by the ß subunit.
The coordination geometry of the iron can be described as trigonal
bipyramidal with Tyrß147 and
Hisß162 serving as axial ligands and
Tyrß108, Hisß160 and a
solventderived ligand (water or hydroxide ion) serving as equatorial
ligands (Figure 2PCD b).
The native enzyme contains a highspin, pentacoordinate FeIII
centre (I). Upon substrate binding, the solventderived ligand and
Tyrß147 are displaced by a bidentate catecholate dianion
(cf. bidentate catecholate monoanion in extradiol
aromaticringcleavage reaction) and the FeIII centre
(II) remains pentacoordinate. The attack of
O2 on the semiquinone radical (III) yields a transient
alkylperoxide radical (IV) which combines with FeII centre
to generate a tridentate alkylperoxo-FeIII complex (V).
Decomposition of compound (V) by a Crigeetype rearrangement
yields muconic anhydride and a nativelike FeIII centre
(VI). Muconic anhydride is subsequently hydrolysed by an
FeIIIbound hydroxide derived from O2
[2].
IARCD in enzyme databases
| ENZYME | LIGAND | BRENDA | UMBBD | Official name | Alternative names |
|---|---|---|---|---|---|
| 1.13.11.1 | 1.13.11.1 | 1.13.11.1 | e0064 | Catechol 1,2dioxygenase | Catechase; chlorocatechol 1,2dioxygenase; 1,2pyrocatechase |
| e0231 | 3,5dichlorocatechol 1,2dioxygenase | ||||
| e0236 | 4chlorocatechol 1,2dioxygenase | ||||
| 1.13.11.3 | 1.13.11.3 | 1.13.11.3 | e0114 | Protocatechuate 3,4dioxygenase | Protocatechuate oxygenase |
| PRINTS ID | PRINTS AC | PROSITE/BLOCKS ID | PROSITE AC | BLOCKS AC |
|---|---|---|---|---|
| INTRADIOL_DIOXYGENAS | PS00083 | BL00083 |
| Protein Superfamily | Pfam | LPFC 3D alignment |
|---|---|---|
| 00181; protocatechuate 3,4dioxygenase |
| PDB | scop | BSM | RELI Base | Header | 2pcd | 2pcd | 2pcd | 2pcd | Protocatechuate 3,4dioxygenase (ß)6 oligomer (pH 8.4, 20 °C); Pseudomonas putida ATCC 23975 |
|---|---|---|---|---|
| 3pca | 3pca | 3pca | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 3,4dihydroxybenzoate and ßmercaptoethanol); Pseudomonas putida ATCC 23975 | |
| 3pcb | 3pcb | 3pcb | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 3hydroxybenzoate and ßmercaptoethanol); Pseudomonas putida ATCC 23975 | |
| 3pcc | 3pcc | 3pcc | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 4hydroxybenzoate and ßmercaptoethanol); Pseudomonas putida ATCC 23975 | |
| 3pcd | 3pcd | 3pcd | Protocatechuate 3,4dioxygenase (ß)6 oligomer (Y447H mutant) (complex with CO32- and ßmercaptoethanol); Pseudomonas putida ATCC 23975 | |
| 3pce | 3pce | 3pce | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 3hydroxyphenylacetate and ßmercaptoethanol); Pseudomonas putida ATCC 23975 | |
| 3pcf | 3pcf | 3pcf | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 3fluoro4hydroxybenzoate and ßmercaptoethanol); Pseudomonas putida ATCC 23975 | |
| 3pch | 3pch | 3pch | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 3chloro4hydroxybenzoate and ßmercaptoethanol); Pseudomonas putida ATCC 23975 | |
| 3pci | 3pci | 3pci | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 3iodo4hydroxybenzoate and ßmercaptoethanol); Pseudomonas putida ATCC 23975 | |
| 3pcj | 3pcj | 3pcj | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 2hydroxyisonicotinic acid Noxide and ßmercaptoethanol); Pseudomonas putida ATCC 23975 | |
| 3pck | 3pck | 3pck | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 6hydroxynicotinic acid Noxide and ßmercaptoethanol); Pseudomonas putida ATCC 23975 | |
| 3pcl | 3pcl | 3pcl | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 2hydroxyisonicotinic acid Noxide and cyanide); Pseudomonas putida ATCC 23975 | |
| 3pcm | 3pcm | 3pcm | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 6hydroxynicotinic acid Noxide and cyanide); Pseudomonas putida ATCC 23975 | |
| 3pcn | 3pcn | 3pcn | Protocatechuate 3,4dioxygenase (ß)6 oligomer (complex with 3,4dihydroxyphenylacetate and ßmercaptoethanol); Pseudomonas putida ATCC 23975 |
References
| Bibliography on structural studies of intradiol aromaticringcleavage dioxygenases |
|
| Reviews on aromaticringcleavage dioxygenases |
