Structural highlights
FunctionTRPB1_THEMA The beta subunit is responsible for the synthesis of L-tryptophan from indole and L-serine. Publication Abstract from PubMedAromatic amino acids and their derivatives are diverse primary and secondary metabolites with critical roles in protein synthesis, cell structure and integrity, defense and signaling. All de novo aromatic amino acid production relies on a set of ancient and highly conserved chemistries. Here we introduce a new enzymatic transformation for L-tyrosine synthesis by demonstrating that the beta-subunit of tryptophan synthase-which natively couples indole and L-serine to form L-tryptophan-can act as a latent 'tyrosine synthase'. A single substitution of a near-universally conserved catalytic residue unlocks activity toward simple phenol analogs and yields exclusive para carbon-carbon bond formation to furnish L-tyrosines. Structural and mechanistic studies show how a new active-site water molecule orients phenols for a nonnative mechanism of alkylation, with additional directed evolution resulting in a net >30,000-fold rate enhancement. This new biocatalyst can be used to efficiently prepare valuable L-tyrosine analogs at gram scales and provides the missing chemistry for a conceptually different pathway to L-tyrosine. The beta-subunit of tryptophan synthase is a latent tyrosine synthase.,Almhjell PJ, Johnston KE, Porter NJ, Kennemur JL, Bhethanabotla VC, Ducharme J, Arnold FH Nat Chem Biol. 2024 May 14. doi: 10.1038/s41589-024-01619-z. PMID:38744987[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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