Structural highlights
5imp is a 4 chain structure with sequence from Aspte. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
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| Ligands: | , , , |
| Related: | 5in8, 5imn, 5imi |
| Gene: | Ari1 (ASPTE) |
| Activity: | Aristolochene synthase, with EC number 4.2.3.9 |
| Resources: | FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT |
Function
[ARIS_ASPTE] Catalyzes the cyclization of trans,trans-farnesyl diphosphate (FPP) to the bicyclic sesquiterpene aristolochene. Produces germacrene A as an enzyme-bound intermediate that is not released by the enzyme, but is further cyclized to produce aristolochene. Aristolochene is the likely parent compound for a number of sesquiterpenoid toxins produced by filamentous fungi.[1] [2]
Publication Abstract from PubMed
Aristolochene synthase (ATAS) is a high-fidelity terpenoid cyclase that converts farnesyl diphosphate exclusively into the bicyclic hydrocarbon aristolochene. Previously determined crystal structures of ATAS complexes revealed trapped active site water molecules that could potentially interact with catalytic intermediates: water "w" hydrogen bonds with S303 and N299, water molecules "w1" and "w2" hydrogen bond with Q151, and a fourth water molecule coordinates to the Mg(2+)C ion. There is no obvious role for water in the ATAS mechanism because the enzyme exclusively generates a hydrocarbon product. Thus, these water molecules are tightly controlled so that they cannot react with carbocation intermediates. Steady-state kinetics and product distribution analyses of eight ATAS mutants designed to perturb interactions with active site water molecules (S303A, S303H, S303D, N299A, N299L, N299A/S303A, Q151H, and Q151E) indicate relatively modest effects on catalysis but significant effects on sesquiterpene product distributions. X-ray crystal structures of S303A, N299A, N299A/S303A, and Q151H mutants reveal minimal perturbation of active site solvent structure. Seven of the eight mutants generate farnesol and nerolidol, possibly resulting from addition of the Mg(2+)C-bound water molecule to the initially formed farnesyl cation, but no products are generated that would suggest enhanced reactivity of other active site water molecules. However, intermediate germacrene A tends to accumulate in these mutants. Thus, apart from the possible reactivity of Mg(2+)C-bound water, active site water molecules in ATAS are not directly involved in the chemistry of catalysis but instead contribute to the template that governs the conformation of the flexible substrate and carbocation intermediates.
Probing the Role of Active Site Water in the Sesquiterpene Cyclization Reaction Catalyzed by Aristolochene Synthase.,Chen M, Chou WK, Al-Lami N, Faraldos JA, Allemann RK, Cane DE, Christianson DW Biochemistry. 2016 May 24;55(20):2864-74. doi: 10.1021/acs.biochem.6b00343. Epub , 2016 May 12. PMID:27172425[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Cane DE, Kang I. Aristolochene synthase: purification, molecular cloning, high-level expression in Escherichia coli, and characterization of the Aspergillus terreus cyclase. Arch Biochem Biophys. 2000 Apr 15;376(2):354-64. PMID:10775423 doi:10.1006/abbi.2000.1734
- ↑ Felicetti B, Cane DE. Aristolochene synthase: mechanistic analysis of active site residues by site-directed mutagenesis. J Am Chem Soc. 2004 Jun 16;126(23):7212-21. PMID:15186158 doi:10.1021/ja0499593
- ↑ Chen M, Chou WK, Al-Lami N, Faraldos JA, Allemann RK, Cane DE, Christianson DW. Probing the Role of Active Site Water in the Sesquiterpene Cyclization Reaction Catalyzed by Aristolochene Synthase. Biochemistry. 2016 May 24;55(20):2864-74. doi: 10.1021/acs.biochem.6b00343. Epub , 2016 May 12. PMID:27172425 doi:http://dx.doi.org/10.1021/acs.biochem.6b00343
