A Caltech Library Service

Direct enzymatic synthesis of a deep-blue fluorescent noncanonical amino acid from azulene and serine

Watkins, Ella J. and Almhjell, Patrick J. and Arnold, Frances H. (2020) Direct enzymatic synthesis of a deep-blue fluorescent noncanonical amino acid from azulene and serine. ChemBioChem, 21 (1-2). pp. 80-83. ISSN 1439-4227. PMCID PMC6980211. doi:10.1002/cbic.201900497.

[img] PDF (PubMed Central) - Accepted Version
See Usage Policy.

[img] PDF - Accepted Version
See Usage Policy.

[img] PDF - Supplemental Material
See Usage Policy.


Use this Persistent URL to link to this item:


We report a simple, one‐step enzymatic synthesis of the blue fluorescent noncanonical amino acid β‐(1‐azulenyl)‐l‐alanine (AzAla). 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.

Item Type:Article
Related URLs:
URLURL TypeDescription CentralArticle
Watkins, Ella J.0000-0002-7365-5791
Almhjell, Patrick J.0000-0003-0977-841X
Arnold, Frances H.0000-0002-4027-364X
Additional Information:© 2019 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim. Manuscript received: August 8, 2019; Accepted manuscript online: September 12, 2019; Version of record online: November 18, 2019. We thank Giovanni Tomaleri for his experimental assistance, Nathaniel Goldberg and Dr. Ben Levin for insightful discussions, and Dr. Tina Boville and Dr. David Romney for valuable contributions to experimental design. We thank Dr. Scott Virgil and the Center for Catalysis and Synthesis. This work was supported by the Rothenberg Innovation Initiative and by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number R01GM125887. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Conflict of Interest: Enzyme variants in this manuscript and enzymatic synthesis of AzAla are the subject of a patent application (P.J.A. inventor).
Funding AgencyGrant Number
Rothenberg Innovation Initiative (RI2)UNSPECIFIED
Subject Keywords:protein engineering; Amino acids; Biocatalysis; Sustainable Chemistry; Aromatic Ions
Issue or Number:1-2
PubMed Central ID:PMC6980211
Record Number:CaltechAUTHORS:20190912-124018949
Persistent URL:
Official Citation:Direct enzymatic synthesis of a deep-blue fluorescent noncanonical amino acid from azulene and serine. E. J. Watkins, P. J. Almhjell, F. H. Arnold, ChemBioChem 2020, 21, 80; doi: 10.1002/cbic.201900497
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98611
Deposited By: Tony Diaz
Deposited On:12 Sep 2019 20:17
Last Modified:09 Feb 2022 23:47

Repository Staff Only: item control page