Phthalate dioxygenase system

 

The phthalate dioxygenase system consists of two proteins: phthalate dioxygenase reductase (PDR) and phthalate dioxygenase (PDO). PDR is a flavoprotein pyridine nucleotide cytochrome reductase (FPNCR). These proteins catalyse the interchange of reducing equivalents between one-electron carriers and the two-electron-carrying nicotinamide dinucleotides. PDR is a fusion protein that has FPNCR and [2Fe-2S] ferredoxin domains, found in flavobacteria, that participate in oxidative metabolism of a variety of substrates. The direction of electron flow is from flavin to the [2Fe-2S] centre. By contrast with most FPNCRs, PDR binds FMN instead of FAD. PDO is a non-hemer iron dependent dioxygenase. The electrons are transferred from PDR to PDO, which then performs the dioxygenase reaction.

 

Reference Protein

Sequences
P33164 UniProt (1.-.-.-)
Q9ZFQ5 UniProt IPR000951 (Sequence Homologues)
Biological species
Burkholderia cepacia (Pseudomonas cepacia) Uniprot
Cofactors
Fmnh2(2-) (1), Di-mu-sulfido-diiron(2+) (2), Iron(3+) (1)
 

Enzyme Reaction (EC:1.14.12.7)

phthalate(2-)
CHEBI:17563ChEBI
+
NADH(2-)
CHEBI:57945ChEBI
+
hydron
CHEBI:15378ChEBI
+
dioxygen
CHEBI:15379ChEBI
→
cis-4,5-dihydroxycyclohexa-2,6-diene-1,2-dicarboxylate(2-)
CHEBI:58237ChEBI
+
NAD(1-)
CHEBI:57540ChEBI
Alternative enzyme names: PDO, Phthalate dioxygenase,

Enzyme Mechanism

Introduction

Phthalate dioxygenase reductase (PDR) is responsible for transferring electrons from NADH to the Rieske centre of phthalate dioxygenase (PDO) via FMN and a Rieske centre in the PDR protein. The PDO Rieske centre then supplies electrons to the mononuclear centre for the oxygenation of substrate. To date, there is very little information on this enzyme system and the exact mechanism of the reaction. There is no crystal structure available for the PDO portion of the system.

Catalytic Residues Roles

UniProt
Asp178 The exact role of this residue is unknown, but it is known to be critical in the communication between the two proteins involved in this system. unknown

Chemical Components

References

  1. Tarasev M et al. (2005), Biochemistry, 44, 6197-6207. Chemistry of the catalytic conversion of phthalate into its cis-dihydrodiol during the reaction of oxygen with the reduced form of phthalate dioxygenase. DOI:10.1021/bi047724y. PMID:15835907.
  2. Tarasev M et al. (2006), Biochemistry, 45, 10208-10216. The "bridging" aspartate 178 in phthalate dioxygenase facilitates interactions between the Rieske center and the iron(II)--mononuclear center. DOI:10.1021/bi060219b. PMID:16922496.
  3. Pinto A et al. (2006), Biochemistry, 45, 9032-9041. Substitutions of the "bridging" aspartate 178 result in profound changes in the reactivity of the Rieske center of phthalate dioxygenase. DOI:10.1021/bi060216z. PMID:16866348.
  4. Tarasev M et al. (2004), Biochemistry, 43, 12799-12808. Rates of the phthalate dioxygenase reaction with oxygen are dramatically increased by interactions with phthalate and phthalate oxygenase reductase. DOI:10.1021/bi0490587. PMID:15461452.
  5. Karplus PA et al. (1994), J Bioenerg Biomembr, 26, 89-99. Structure-function relations for ferredoxin reductase. PMID:8027025.
  6. Correll CC et al. (1992), Science, 258, 1604-1610. Phthalate dioxygenase reductase: a modular structure for electron transfer from pyridine nucleotides to [2Fe-2S]. DOI:10.1126/science.1280857. PMID:1280857.

Step 1.

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Catalytic Residues Roles

Residue Roles
Asp178 unknown

Chemical Components

Step 1.

Contributors

Craig Porter, Gemma L. Holliday