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| - | Indole-3-glycerol-phosphate (IGP) is cleaved by the tryptophan synthase α-subunit (TSA) to indole and glyceraldehyde-3-phosphate (GDP) This is known as the α-reaction. The alpha reaction is reversible. Then indole is transported via a 30 Å intermolecular tunnel to the tryptophan synthase β-subunits (TSB) that catalyze the condensation of indole and serine to tryptophan. This is known as the β-reaction and it is a pyridoxal-5-phosphate (PLP) dependent reaction. | + | Indole-3-glycerol-phosphate (IGP) is cleaved by the tryptophan synthase α-subunit (TSA) to indole and glyceraldehyde-3-phosphate (GDP) This is known as the α-reaction. The alpha reaction is reversible. Then indole is transported via a 30 Å intermolecular tunnel to the tryptophan synthase β-subunits (TSB) that catalyze the condensation of indole and serine to tryptophan. This is known as the β-reaction and it is a pyridoxal-5-phosphate (PLP) dependent reaction. <ref name="cite7">http://tryptophan.net/Trpsynthase/Tryptophan%20Synthase.html</ref> |
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Tryptophan Synthase
Tryptophan synthase is an enzyme that catalyzes the final two steps in the biosynthesis of tryptophan. It is commonly found in Eubacteria, Archaebacteria, Protista, Fungi, and Plantae. However, it is absent from Animalia. [1]
Tryptophan synthase is a classic enzyme that channels a metabolic intermediate, indole.
Contents |
General Information
Gene Name: trpA, trpB[2]
Organism: Salmonella typhimurium (strain LT2) [2]
Classification: Lyase [3]
Length: trpA: 268 AA [2] trpB: 397 AA [2]
Molecular Weight: 72012.45 Da [4]
Isoelectric Point: 5.62 [5]
Chains: A, B [2]
Ligands: Sodium Ion ([1]), pyridoxal-5'-phosphate ([2])[3]
Enzyme Structure
Hydrophobic channel: The α and β active sites are separated by a 30 Å long hydrophobic channel contained within the enzyme allowing for the diffusion of indole. If the channel did not exist, the indole formed at an α active site would quickly diffuse away and be lost to the cell as it is hydrophobic and can easily cross membranes. As such, the channel is essential for enzyme complex function[6]
Sequence of TrpA and Trp B
Alpha Subunit
Beta Subunit
Enzyme Mechanism
Indole-3-glycerol-phosphate (IGP) is cleaved by the tryptophan synthase α-subunit (TSA) to indole and glyceraldehyde-3-phosphate (GDP) This is known as the α-reaction. The alpha reaction is reversible. Then indole is transported via a 30 Å intermolecular tunnel to the tryptophan synthase β-subunits (TSB) that catalyze the condensation of indole and serine to tryptophan. This is known as the β-reaction and it is a pyridoxal-5-phosphate (PLP) dependent reaction. [7]
References
- ↑ http://en.wikipedia.org/wiki/Tryptophan_synthase
- ↑ 2.0 2.1 2.2 2.3 2.4 http://www.uniprot.org/uniprot/P00929
- ↑ 3.0 3.1 http://oca.weizmann.ac.il/oca-bin/ocashort
- ↑ http://www.rcsb.org/pdb/explore.do?structureId=1QOP
- ↑ http://mips.helmholtz-muenchen.de/genre/proj/FGDB/singleGeneReport.html?entry=FGSG_10743
- ↑ http://www.annualreviews.org/doi/abs/10.1146/annurev.biochem.70.1.149
- ↑ http://tryptophan.net/Trpsynthase/Tryptophan%20Synthase.html
