IUBMB Enzyme Nomenclature


Accepted name: tryptophan synthase

Reaction: L-serine + 1-C-(indol-3-yl)glycerol 3-phosphate = L-tryptophan + D-glyceraldehyde 3-phosphate + H2O (overall reaction)
(1a) 1-C-(indol-3-yl)glycerol 3-phosphate = indole + D-glyceraldehyde 3-phosphate
(1b) L-serine + indole = L-tryptophan + H2O

For diagram of reaction click here and mechanism click here

Other name(s): L-tryptophan synthetase; indoleglycerol phosphate aldolase; tryptophan desmolase; tryptophan synthetase; L-serine hydro-lyase (adding indoleglycerol-phosphate)

Systematic name: L-serine hydro-lyase [adding 1-C-(indol-3-yl)glycerol 3-phosphate, L-tryptophan and glyceraldehyde-3-phosphate-forming]

Comments: A pyridoxal-phosphate protein. The α-subunit catalyses the conversion of 1-C-(indol-3-yl)glycerol 3-phosphate to indole and glyceraldehyde 3-phosphate (this reaction was listed formerly as EC The indole migrates to the β-subunit where, in the presence of pyridoxal 5'-phosphate, it is combined with L-serine to form L-tryptophan. In some organisms this enzyme is part of a multifunctional protein that also includes one or more of the enzymes EC (anthranilate phosphoribosyltransferase), EC (indole-3-glycerol-phosphate synthase), EC (anthranilate synthase) and EC (phosphoribosylanthranilate isomerase). In thermophilic organisms, where the high temperature enhances diffusion and causes the loss of indole, a protein similar to the β subunit can be found (EC That enzyme cannot combine with the α unit of EC to form a complex.

Links to other databases: BRENDA, EXPASY, GTD, KEGG, Metacyc, PDB, CAS registry number: 9014-52-2


1. Crawford, I.P. and Yanofsky, C. On the separation of the tryptophan synthetase of Escherichia coli into two protein components. Proc. Natl. Acad. Sci. USA 44 (1958) 1161-1170. [PMID: 16590328]

2. Creighton, T.E. and Yanofsky, C. Chorismate to tryptophan (Escherichia coli) - anthranilate synthetase, PR transferase, PRA isomerase, InGP synthetase, tryptophan synthetase. Methods Enzymol. 17A (1970) 365-380.

3. Hütter, R., Niederberger, P. and DeMoss, J.A. Tryptophan synthetic genes in eukaryotic microorganisms. Annu. Rev. Microbiol. 40 (1986) 55-77. [PMID: 3535653]

4. Hyde, C.C., Ahmed, S.A., Padlan, E.A., Miles, E.W. and Davies, D.R. Three-dimensional structure of the tryptophan synthase α2β2 multienzyme complex from Salmonella typhimurium. J. Biol. Chem. 263 (1988) 17857-17871. [PMID: 3053720]

5. Woehl, E. and Dunn, M.F. Mechanisms of monovalent cation action in enzyme catalysis: the tryptophan synthase α-, β-, and αβ-reactions. Biochemistry 38 (1999) 7131-7141. [PMID: 10353823]

[EC created 1961, modified 1976, modified 2002, modified 2011]

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