Biosynthesis of l‐4‐Chlorokynurenine, an Antidepressant Prodrug and a Non‐Proteinogenic Amino Acid Found in Lipopeptide Antibiotics. Issue 25 (13th May 2019)

• Record Type: Journal Article
• Authors: Luhavaya, Hanna; Sigrist, Renata; Chekan, Jonathan R.; McKinnie, Shaun M. K.; Moore, Bradley S.
• Is Part Of: Angewandte Chemie international edition. Volume 58:Issue 25(2019)
• Page Start: 8394
• Page End: 8399
• Publication Date: 2019-05-13
• Subjects: biocatalysis -- biosynthesis -- chlorokynurenine -- halogenation -- natural products; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201901571
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: l ‐4‐Chlorokynurenine (l ‐4‐Cl‐Kyn) is a neuropharmaceutical drug candidate that is in development for the treatment of major depressive disorder. Recently, this amino acid was naturally found as a residue in the lipopeptide antibiotic taromycin. Herein, we report the unprecedented conversion of l ‐tryptophan into l ‐4‐Cl‐Kyn catalyzed by four enzymes in the taromycin biosynthetic pathway from the marine bacterium Saccharomonospora sp. CNQ‐490. We used genetic, biochemical, structural, and analytical techniques to establish l ‐4‐Cl‐Kyn biosynthesis, which is initiated by the flavin‐dependent tryptophan chlorinase Tar14 and its flavin reductase partner Tar15. This work revealed the first tryptophan 2, 3‐dioxygenase (Tar13) and kynurenine formamidase (Tar16) enzymes that are selective for chlorinated substrates. The substrate scope of Tar13, Tar14, and Tar16 was examined and revealed intriguing promiscuity, thereby opening doors for the targeted engineering of these enzymes as useful biocatalysts. Abstract : Two paths diverge : The biosynthetic route to neuroactive l ‐4‐chlorokynurenine was revealed by using a combination of in vitro experiments, X‐ray crystallography, and CRISPR/Cas9‐mediated gene deletion. Tar13 and Tar16 are the first reported tryptophan 2, 3‐dioxygenase and kynurenine formamidase homologues, respectively, that preferentially accept chlorinated substrates. The enzymes characterized in this work hold promise for use in chemoenzymatic synthesis.