title: Discovery of a substrate selectivity switch in tyrosine ammonia-lyase, a member of the aromatic amino acid lyase family.
abstract: Tyrosine ammonia-lyase (TAL) is a recently described member of the aromatic amino acid lyase family, which also includes phenylalanine (PAL) and histidine ammonia-lyases (HAL). TAL is highly selective for L-tyrosine, and synthesizes 4-coumaric acid as a protein cofactor or antibiotic precursor in microorganisms. In this report, we identify a single active site residue important for substrate selection in this enzyme family. Replacing the active site residue His89 with Phe in TAL completely switched its substrate selectivity from tyrosine to phenylalanine, thereby converting it into a highly active PAL. When a corresponding mutation was made in PAL, the enzyme lost PAL activity and gained TAL activity. The discovered substrate selectivity switch is a rare example of a complete alteration of substrate specificity by a single point mutation. We also show that the identity of the amino acid at the switch position can serve as a guide to predict substrate specificities of annotated aromatic amino acid lyases in genome sequences.
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 1479 Gortner Avenue, St. Paul, Minnesota 55108, USA.
authors.forename: Kevin T
authors.initials: KT
authors.lastname: Watts
authors.forename: Benjamin N
authors.initials: BN
authors.lastname: Mijts
authors.forename: Pyung Cheon
authors.initials: PC
authors.lastname: Lee
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Manning
authors.forename: Claudia
authors.initials: C
authors.lastname: Schmidt-Dannert
mesh_terms: D000595:Amino Acid Sequence; D024322:Amino Acids, Aromatic / Q000737:chemistry* / Q000378:metabolism; D000642:Ammonia-Lyases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D001419:Bacteria / Q000201:enzymology; D001665:Binding Sites; D002478:Cells, Cultured; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D024322:Amino Acids, Aromatic; D000642:Ammonia-Lyases; C023208:L-tyrosine ammonia-lyase