InterPro domain: IPR006654

Tryptophan synthase catalyses the last step in the biosynthesis of tryptophan [ 1 , 2 ]: L-serine + 1-(indol-3-yl)glycerol 3-phosphate = L-tryptophan + glyceraldehyde 3-phosphate + H ₂ O It has two functional domains, each found in bacteria and plants on a separate subunit: alpha chain ( IPR002028 ) is for the aldol cleavage of indoleglycerol phosphate to indole and glyceraldehyde 3-phosphate and beta chain is for the synthesis of tryptophan from indole and serine. In fungi the two domains are fused together on a single multifunctional protein [ 3 ].

The beta chain of the enzyme, represented here, requires pyridoxal-phosphate as a cofactor. The pyridoxal-phosphate group is attached to a lysine residue. The region around this lysine residue also contains two histidine residues which are part of the pyridoxal-phosphate binding site.

1. Evolution of a biosynthetic pathway: the tryptophan paradigm. Annu. Rev. Microbiol. 43, 567-600
2. The tryptophan synthase multienzyme complex: exploring structure-function relationships with X-ray crystallography and mutagenesis. Biotechnology (N.Y.) 8, 27-32
3. A gene encoding the tryptophan synthase beta subunit of Arabidopsis thaliana. Proc. Natl. Acad. Sci. U.S.A. 86, 4604-8