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 18.104.22.168) 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 22.214.171.124.
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]