Chloromuconate cycloisomerase
Bacterial muconate lactonizing enzymes (MLEs) catalyze the conversion of cis,cis-muconate as a part of the beta-ketoadipate pathway. Some MLEs, including the enzyme annotated here, are also able to dehalogenate chlorinated muconate to form five-member furan rings. This enzyme catalyses several cyclisation and dehalogenation reactions.
Reference Protein and Structure
- Sequence
-
P05404
(5.5.1.7)
(Sequence Homologues)
(PDB Homologues)
- Biological species
-
Ralstonia eutropha JMP134 (Bacteria)
- PDB
-
2chr
- A RE-EVALUATION OF THE CRYSTAL STRUCTURE OF CHLOROMUCONATE CYCLOISOMERASE
(3.0 Å)
- Catalytic CATH Domains
-
3.20.20.120
(see all for 2chr)
- Cofactors
- Manganese(2+) (1)
Enzyme Reaction (EC:5.5.1.7)
+
→
+
Alternative enzyme names: Muconate cycloisomerase II, 2-chloro-2,5-dihydro-5-oxofuran-2-acetate lyase (decyclizing), 2-chloro-2,5-dihydro-5-oxofuran-2-acetate lyase (ring-opening),
Enzyme Mechanism
Introduction
O'6 undergoes an intramolecular addition at the C4 double bond with concomitant deprotonation of Glu323.
Calculations of the active site polarity suggest a degree of positive charge. This is thought to be neutralised on the elimination of chloride ion, and therefore drive the reaction towards the furan product.
Catalytic Residues Roles
| UniProt | PDB* (2chr) | ||
| Glu323 | Glu323A | Acts as the general acid/base. | activator, hydrogen bond donor, proton acceptor, proton donor |
| Asp194, Glu220, Asp245 | Asp194A, Glu220A, Asp245A | Forms the manganese binding site. | metal ligand |
| Lys269, Lys165, Lys163 | Lys269A, Lys165A, Lys163A | Helps stabilise the negatively charged intermediates and transition states. | hydrogen bond donor, electrostatic stabiliser |
*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
intramolecular nucleophilic addition, intermediate formation, overall reactant used, proton transfer, rate-determining step, bimolecular eliminationReferences
- Neidhart DJ et al. (1990), Nature, 347, 692-694. Mandelate racemase and muconate lactonizing enzyme are mechanistically distinct and structurally homologous. DOI:10.1038/347692a0. PMID:2215699.
- Kajander T et al. (2003), Protein Sci, 12, 1855-1864. The structure ofPseudomonasP51 Cl-muconate lactonizing enzyme: Co-evolution of structure and dynamics with the dehalogenation function. DOI:10.1110/ps.0388503. PMID:12930985.
- Kaulmann U et al. (2001), J Bacteriol, 183, 4551-4561. Mechanism of Chloride Elimination from 3-Chloro- and 2,4-Dichloro-cis,cis-Muconate: New Insight Obtained from Analysis of Muconate Cycloisomerase Variant CatB-K169A. DOI:10.1128/jb.183.15.4551-4561.2001. PMID:11443090.
- Schell U et al. (1999), Proteins, 34, 125-136. Structural basis for the activity of two muconate cycloisomerase variants toward substituted muconates. DOI:10.1002/(sici)1097-0134(19990101)34:1<125::aid-prot10>3.3.co;2-p. PMID:10336378.
- Vollmer MD et al. (1998), Appl Environ Microbiol, 64, 3290-3299. Substrate specificity of and product formation by muconate cycloisomerases: an analysis of wild-type enzymes and engineered variants. PMID:9726873.
- Hasson MS et al. (1998), Proc Natl Acad Sci U S A, 95, 10396-10401. Evolution of an enzyme active site: The structure of a new crystal form of muconate lactonizing enzyme compared with mandelate racemase and enolase. DOI:10.1073/pnas.95.18.10396. PMID:9724714.
- Kleywegt GJ et al. (1996), Acta Crystallogr D Biol Crystallogr, 52, 858-863. A re-evaluation of the crystal structure of chloromuconate cycloisomerase. DOI:10.1107/s0907444995008936. PMID:15299651.
- Solyanikova IP et al. (1995), J Bacteriol, 177, 2821-2826. Characterization of muconate and chloromuconate cycloisomerase from Rhodococcus erythropolis 1CP: indications for functionally convergent evolution among bacterial cycloisomerases. PMID:7751292.
- Schmidt E et al. (1980), Biochem J, 192, 339-347. Chemical structure and biodegradability of halogenated aromatic compounds. Conversion of chlorinated muconic acids into maleoylacetic acid. DOI:10.1042/bj1920339. PMID:7305906.
Step 1. O'6 undergoes an intramolecular addition at the C4 double bond with concomitant deprotonation of Glu323.
Download: Image, Marvin FileCatalytic Residues Roles
| Residue | Roles |
|---|---|
| Asp194A | metal ligand |
| Glu220A | metal ligand |
| Asp245A | metal ligand |
| Lys163A | hydrogen bond donor, electrostatic stabiliser |
| Lys269A | hydrogen bond donor, electrostatic stabiliser |
| Lys165A | hydrogen bond donor, electrostatic stabiliser |
| Glu323A | activator, hydrogen bond donor |
| Glu323A | proton donor |
Chemical Components
ingold: intramolecular nucleophilic addition, intermediate formation, overall reactant used, proton transfer, rate-determining step
Step 2. Glu323 abstracts a proton from the substrate, resulting in the elimination of the chloride ion.
Download: Image, Marvin FileCatalytic Residues Roles
| Residue | Roles |
|---|---|
| Asp194A | metal ligand |
| Glu220A | metal ligand |
| Asp245A | metal ligand |
| Lys163A | electrostatic stabiliser |
| Lys165A | electrostatic stabiliser |
| Lys269A | electrostatic stabiliser |
| Glu323A | proton acceptor |
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