Sandbox Reserved 769

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This Sandbox is Reserved from Sep 25, 2013, through Mar 31, 2014 for use in the course "BCH455/555 Proteins and Molecular Mechanisms" taught by Michael B. Goshe at the North Carolina State University. This reservation includes Sandbox Reserved 299, Sandbox Reserved 300 and Sandbox Reserved 760 through Sandbox Reserved 779.

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spinqualitylabelsall models Structure of a tryptophan synthase quinonoid intermediate. Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

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 1 Tryptophan Synthase 2 General Information 3 Enzyme Structure 4 Enzyme Mechanism 5 References

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]

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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

1. ↑ http://en.wikipedia.org/wiki/Tryptophan_synthase
2. ↑ ^{2.0 2.1 2.2 2.3 2.4} http://www.uniprot.org/uniprot/P00929
3. ↑ ^{3.0 3.1} http://oca.weizmann.ac.il/oca-bin/ocashort
4. ↑ http://www.rcsb.org/pdb/explore.do?structureId=1QOP
5. ↑ http://mips.helmholtz-muenchen.de/genre/proj/FGDB/singleGeneReport.html?entry=FGSG_10743
6. ↑ http://www.annualreviews.org/doi/abs/10.1146/annurev.biochem.70.1.149
7. ↑ http://tryptophan.net/Trpsynthase/Tryptophan%20Synthase.html