IUBMB Enzyme Nomenclature


Accepted name: tryptophan synthase (indole-salvaging)

Reaction: L-serine + indole = L-tryptophan + H2O

Other name(s): tryptophan synthase β2

Systematic name: L-serine hydro-lyase [adding indole, L-tryptophan-forming]

Comments: Most mesophilic bacteria have a multimeric tryptophan synthase complex (EC that forms L-tryptophan from L-serine and 1-C-(indol-3-yl)glycerol 3-phosphate via an indole intermediate. This intermediate, which is formed by the α subunits, is transferred in an internal tunnel to the β units, which convert it to tryptophan. In thermophilic organisms the high temperature enhances diffusion and causes the loss of indole. This enzyme, which does not combine with the α unit to form a complex, salvages the lost indole back to L-tryptophan. It has a much lower Km for indole than the β subunit of EC

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Hettwer, S. and Sterner, R. A novel tryptophan synthase β-subunit from the hyperthermophile Thermotoga maritima. Quaternary structure, steady-state kinetics, and putative physiological role. J. Biol. Chem. 277 (2002) 8194-8201. [PMID: 11756459]

[EC created 2011]

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