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Updated: Feb 17, 2026

Chemical Modification of the Tryptophan Residue in a Recombinant Ca2+-ATPase N-domain for Studying Tryptophan-ANS FRET
Published on: October 9, 2021
Mechanistic Studies on Tryptophan Lyase (NosL): Identification of Cyanide as a Reaction Product
Dhananjay M Bhandari1, Dmytro Fedoseyenko1, Tadhg P Begley1
1Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States.
Abstract:
Tryptophan lyase (NosL) catalyzes the formation of 3-methylindole-2-carboxylic acid and 3-methylindole from l-tryptophan. In this paper, we provide evidence supporting a formate radical intermediate and demonstrate that cyanide is a byproduct of the NosL-catalyzed reaction with l-tryptophan. These experiments require a major revision of the NosL mechanism and uncover an unanticipated connection between NosL and HydG, the radical SAM enzyme that forms cyanide and carbon monoxide from tyrosine during the biosynthesis of the metallo-cluster of the [Fe-Fe] hydrogenase.
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