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Direct Enzymatic Synthesis of a Deep‐Blue Fluorescent Noncanonical Amino Acid from Azulene and Serine
Author(s) -
Watkins Ella J.,
Almhjell Patrick J.,
Arnold Frances H.
Publication year - 2020
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.201900497
Subject(s) - azulene , chemistry , tryptophan synthase , serine , glycine , indole test , enzyme , alanine , amino acid , aromatic amino acids , nucleophile , stereochemistry , biochemistry , tryptophan , combinatorial chemistry , catalysis , photochemistry
We report a simple, one‐step enzymatic synthesis of the blue fluorescent noncanonical amino acid β‐(1‐azulenyl)‐ l ‐alanine (AzAla). By using an engineered tryptophan synthase β‐subunit (TrpB), stereochemically pure AzAla can be synthesized at scale starting from commercially available azulene and l ‐serine. Mutation of a universally conserved catalytic glutamate in the active site to glycine has only a modest effect on native activity with indole but abolishes activity on azulene, suggesting that this glutamate activates azulene for nucleophilic attack by stabilization of the aromatic ion.