title: Tryptophan Lyase (NosL): Mechanistic Insights from Substrate Analogues and Mutagenesis.
abstract: NosL is a member of a family of radical S-adenosylmethionine enzymes that catalyze the cleavage of the Cα-Cβ bond of aromatic amino acids. In this paper, we describe a set of experiments with substrate analogues and mutants for probing the early steps of the NosL mechanism. We provide biochemical evidence in support of the structural studies showing that the 5'-deoxyadenosyl radical abstracts a hydrogen atom from the amino group of tryptophan. We demonstrate that d-tryptophan is a substrate for NosL but shows relaxed regio control of the first β-scission reaction. Mutagenesis studies confirm that Arg323 is important for controlling the regiochemistry of the β-scission reaction and that Ser340 binds the substrate by hydrogen bonding to the indolic N1 atom.
authors.forename: Dhananjay M
authors.initials: DM
authors.lastname: Bhandari
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
authors.affiliation: ‡Metalloproteins Unit, Institut de Biologie Structurale UMR5075, CEA, CNRS, Université Grenoble-Alpes 71, Avenue des Martyrs, CS 10090, 38044 Grenoble cedex 9, France.
authors.forename: Yvain
authors.initials: Y
authors.lastname: Nicolet
authors.affiliation: ‡Metalloproteins Unit, Institut de Biologie Structurale UMR5075, CEA, CNRS, Université Grenoble-Alpes 71, Avenue des Martyrs, CS 10090, 38044 Grenoble cedex 9, France.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Fontecilla-Camps
authors.forename: Tadhg P
authors.initials: TP
authors.lastname: Begley
mesh_terms: D019943:Amino Acid Substitution; D001419:Bacteria / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019755:Carbon-Carbon Lyases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D013379:Substrate Specificity; D014364:Tryptophan / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D014364:Tryptophan; D019755:Carbon-Carbon Lyases