Tryptophan synthase: a mine for enzymologists
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- Raboni, S., Bettati, S. & Mozzarelli, A. Cell. Mol. Life Sci. (2009) 66: 2391. doi:10.1007/s00018-009-0028-0
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Tryptophan synthase is a pyridoxal 5′-phosphate-dependent α2β2 complex catalyzing the last two steps of tryptophan biosynthesis in bacteria, plants and fungi. Structural, dynamic and functional studies, carried out over more than 40 years, have unveiled that: (1) α- and β-active sites are separated by about 20 Å and communicate via the selective stabilization of distinct conformational states, triggered by the chemical nature of individual catalytic intermediates and by allosteric ligands; (2) indole, formed at α-active site, is intramolecularly channeled to the β-active site; and (3) naturally occurring as well as genetically generated mutants have allowed to pinpoint functional and regulatory roles for several individual amino acids. These key features have made tryptophan synthase a text-book case for the understanding of the interplay between chemistry and conformational energy landscapes.
KeywordsEnzyme catalysis Pyridoxal 5′-phosphate Conformational changes Tryptophan X-ray crystallography
Indole 3-propanol phosphate