TrpB2 enzymes are O-phospho-l-serine dependent tryptophan synthases

Biochemistry. 2014 Sep 30;53(38):6078-83. doi: 10.1021/bi500977y. Epub 2014 Sep 17.


The rapid increase of the number of sequenced genomes asks for the functional annotation of the encoded enzymes. We used a combined computational-structural approach to determine the function of the TrpB2 subgroup of the tryptophan synthase β chain/β chain-like TrpB1-TrpB2 family (IPR023026). The results showed that TrpB2 enzymes are O-phospho-l-serine dependent tryptophan synthases, whereas TrpB1 enzymes catalyze the l-serine dependent synthesis of tryptophan. We found a single residue being responsible for the different substrate specificities of TrpB1 and TrpB2 and confirmed this finding by mutagenesis studies and crystallographic analysis of a TrpB2 enzyme with bound O-phospho-l-serine.

MeSH terms

  • Catalytic Domain
  • Cloning, Molecular
  • Computational Biology
  • Crystallization
  • Escherichia coli
  • Gene Expression Regulation, Bacterial / physiology
  • Protein Conformation
  • Substrate Specificity
  • Sulfolobus / enzymology
  • Tryptophan / biosynthesis
  • Tryptophan Synthase / chemistry
  • Tryptophan Synthase / classification
  • Tryptophan Synthase / genetics
  • Tryptophan Synthase / metabolism*


  • Tryptophan
  • Tryptophan Synthase