Sequence similarities between tryptophan synthase beta subunit and other pyridoxal-phosphate-dependent enzymes.

On the basis of 8 tryptophan synthase beta subunits (EC 4.2.1.20) consensus patterns were constructed comprising two conserved motifs. Screening of the SWISSPROT protein sequence database with these patterns indicates similarities with O-acetylserine sulfhydrolases (EC 4.2.99.8), threonine synthases (EC 4.2.99.2), L- and D-serine dehydratases (EC 4.2.1.13/EC 4.2.1.14) and threonine dehydratases (EC 4.2.1.16). Using multiple alignment procedures the similar regions could be extended. In connection with their pyridoxal-phosphate-binding-capacity and their positions in biochemical pathways evolutionary relationships among these enzymes are discussed.