| Type: | Active_site | Name: | Tryptophan synthase, alpha chain, active site |
| Description: | Tryptophan synthase () catalyses the last step in the biosynthesis of tryptophan: the conversion of indoleglycerol phosphate and serine, to tryptophan and glyceraldehyde 3-phosphate [, ].Tryptophan synthetase has two functional domains: the alpha chain for the aldol cleavage of indoleglycerol phosphate to indole and glyceraldehyde 3-phosphate and the beta chain () for the synthesis of tryptophan from indole and serine. In bacteria and plants [], each domain is found on a separate subunit (alpha and beta chains), while in fungi the two domains are fused together on a single multifunctional protein. In Escherichia coli, the 2 subunits, A and B, are encoded by the trpA and trpB genes respectively. In fungi the two domains are fused together in a single multifunctional protein, in the order: (NH2-A-B-COOH) [, ]. The two domains of the Neurospora crassapolypeptide are linked by a connector of 54-amino acid residues that has less than 25% identity to the 45-residue connector of the Saccharomyces cerevisiae(Baker's yeast) polypeptide. Two acidic residues are believed to serve as proton donors/acceptors in the enzyme's catalytic mechanism.This entry represents a motif based around active site residues of the alpha chain. This motif contains three conserved acidic residues, where the first and the third acidic residues are believed to serve as proton donors/acceptors in the enzyme's catalytic mechanism []. | Short Name: | Trp_synthase_alpha_AS |
