title: Synthesis of β-Branched Tryptophan Analogues Using an Engineered Subunit of Tryptophan Synthase.
abstract: We report that l-threonine may substitute for l-serine in the β-substitution reaction of an engineered subunit of tryptophan synthase from Pyrococcus furiosus, yielding (2S,3S)-β-methyltryptophan (β-MeTrp) in a single step. The trace activity of the wild-type β-subunit on this substrate was enhanced more than 1000-fold by directed evolution. Structural and spectroscopic data indicate that this increase is correlated with stabilization of the electrophilic aminoacrylate intermediate. The engineered biocatalyst also reacts with a variety of indole analogues and thiophenol for diastereoselective C-C, C-N, and C-S bond-forming reactions. This new activity circumvents the 3-enzyme pathway that produces β-MeTrp in nature and offers a simple and expandable route to preparing derivatives of this valuable building block.
authors.affiliation: Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Herger
authors.affiliation: Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: van Roye
authors.affiliation: Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States.
authors.forename: David K
authors.initials: DK
authors.lastname: Romney
authors.affiliation: Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States.
authors.forename: Sabine
authors.initials: S
authors.lastname: Brinkmann-Chen
authors.affiliation: Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Buller
authors.affiliation: Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States.
authors.forename: Frances H
authors.initials: FH
authors.lastname: Arnold
mesh_terms: D019943:Amino Acid Substitution; D008958:Models, Molecular; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D020027:Pyrococcus furiosus / Q000201:enzymology; D014364:Tryptophan; D014367:Tryptophan Synthase / Q000737:chemistry*
chemical_list: D021122:Protein Subunits; D014364:Tryptophan; D014367:Tryptophan Synthase