Brefeldin A esterase
Brefeldin A esterase (BFAE), a detoxifying enzyme isolated from Bacillus subtilis, hydrolyses and inactivates BFA, a potent fungal inhibitor of intracellular vesicle-dependent secretory transport and poliovirus RNA replication. BFAE has high sequence homology to the mammalian hormone sensitive lipase (HSL), thus is thought to be a member of the HSL family.
Reference Protein and Structure
- Sequence
-
O68884
(Sequence Homologues)
(PDB Homologues)
- Biological species
-
Bacillus subtilis (Bacteria)
- PDB
-
1jkm
- BREFELDIN A ESTERASE, A BACTERIAL HOMOLOGUE OF HUMAN HORMONE SENSITIVE LIPASE
(1.85 Å)
- Catalytic CATH Domains
-
3.40.50.1820
(see all for 1jkm)
Enzyme Mechanism
Introduction
The enzyme contains a catalytic triad Ser202-His338-Asp308. The mechanism is believed to follow that of a typical esterase. Ser202 is deprotonated by His338 and subsequently attacks the carbonyl moiety in the ester linkage. The tetrahedral intermediate collapses and the negatively charged oxygen deprotonates His338 to form an alcohol functional group. His338 then deprotonates a water molecule to form a nucleophile, which subsequently attacks the carbonyl moiety, forming a second tetrahedral intermediate. The collapse of this results in Ser202 being eliminated as a leaving group and a carboxylic acid function group being formed resulting in the products of hydrolysis.
Catalytic Residues Roles
| UniProt | PDB* (1jkm) | ||
| Ser202 | Ser202(193)A | Part of the catalytic Ser-His-Asp triad. After deprotonation forms a nucleophile, which initiates attack on the ester linkage of Brefeldin A via nucleophilic addition-elimination. | covalent catalysis, proton shuttle (general acid/base) |
| Asp308 | Asp308(299)A | Part of the catalytic Ser-His-Asp triad. Hydrogen bonded to His338 to aid its function as a general acid/base. | modifies pKa, electrostatic stabiliser |
| His338 | His338(329)A | Part of the catalytic Ser-His-Asp triad. Acts as a general acid/base. Abstracts a proton from Ser202 and a water molecule to form a nucleophiles for attack on the carbonyl group. Protonates the leaving groups from collapse of the tetrahedral intermediates. | proton shuttle (general acid/base), electrostatic stabiliser |
| Tyr233, Tyr238 | Tyr233(224)A, Tyr238(229)A | Forms an aromatic sandwich with the substrate and other tyrosine residue. | electrostatic stabiliser |
| Gly127 (main-N), Gly128 (main-N) | Gly127(118)A (main-N), Gly128(119)A (main-N) | The main chain amides form the oxyanion hole. | electrostatic stabiliser |
Chemical Components
References
- Wei Y et al. (1999), Nat Struct Biol, 6, 340-345. Crystal structure of brefeldin A esterase, a bacterial homolog of the mammalian hormone-sensitive lipase. DOI:10.1038/7576. PMID:10201402.
- Huang J et al. (2016), Sci Rep, 6, 28550-. Structural insights of a hormone sensitive lipase homologue Est22. DOI:10.1038/srep28550. PMID:27328716.
- Zarafeta D et al. (2016), Sci Rep, 6, 38886-. Metagenomic mining for thermostable esterolytic enzymes uncovers a new family of bacterial esterases. DOI:10.1038/srep38886. PMID:27991516.
- Byun JS et al. (2007), BMC Struct Biol, 7, 47-. Crystal structure of hyperthermophilic esterase EstE1 and the relationship between its dimerization and thermostability properties. DOI:10.1186/1472-6807-7-47. PMID:17625021.
- De Simone G et al. (2000), J Mol Biol, 303, 761-771. A snapshot of a transition state analogue of a novel thermophilic esterase belonging to the subfamily of mammalian hormone-sensitive lipase. DOI:10.1006/jmbi.2000.4195. PMID:11061974.
Catalytic Residues Roles
| Residue | Roles |
|---|---|
| Ser202(193)A | covalent catalysis, proton shuttle (general acid/base) |
| His338(329)A | proton shuttle (general acid/base) |
| Asp308(299)A | modifies pKa, electrostatic stabiliser |
| His338(329)A | electrostatic stabiliser |
| Gly127(118)A (main-N) | electrostatic stabiliser |
| Gly128(119)A (main-N) | electrostatic stabiliser |
| Tyr233(224)A | electrostatic stabiliser |
| Tyr238(229)A | electrostatic stabiliser |