title: Arabidopsis amidase 1, a member of the amidase signature family.
abstract: Amidase 1 (AMI1), a specific indole-3-acetamide amidohydrolase, is an Arabidopsis thaliana amidase signature enzyme that catalyzes the synthesis of indole-3-acetic acid from indole-3-acetamide. Amidase signature family members catalyze a diverse range of enzymatic reactions and are found widespread in nature, for instance in bacteria, mammals, and plants. At the protein level, the family members share a conserved stretch of approximately 50-130 amino acids, the name-giving amidase signature. Elucidation of the crystal structures of a mammalian fatty acid amide hydrolase and the bacterial malonamidase E2 revealed an unusual Ser-cisSer-Lys catalytic triad in proteins of this family. In addition, other members, such as the amidase from Rhodococcus rhodochrous strain J1 or Sulfolobus solfataricus, seem to use an accessory Cys-cisSer-Lys center. AMI1 possesses all conserved amino-acid residues of the Ser-cisSer-Lys triad, but lacks the CX(3)C motif and therefore the Cys-cisSer-Lys catalytic site. Using a set of point-mutated variants of AMI1 and chemical modifications, we analyzed the relative importance of single amino-acid residues of AMI1 with respect to substrate conversion. These experiments revealed that a specific serine residue, Ser137, is essential for AMI1 enzymatic activity. We also report structural and functional differences of AMI1 from other amidase signature enzymes.
authors.affiliation: Lehrstuhl für Pflanzenphysiologie, Ruhr-Universität Bochum, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Neu
authors.forename: Thomas
authors.initials: T
authors.lastname: Lehmann
authors.forename: Skander
authors.initials: S
authors.lastname: Elleuche
authors.forename: Stephan
authors.initials: S
authors.lastname: Pollmann
mesh_terms: D000581:Amidohydrolases / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology*; D020134:Catalytic Domain; D017124:Conserved Sequence; D007210:Indoleacetic Acids / Q000737:chemistry; D008954:Models, Biological; D008969:Molecular Sequence Data; D005810:Multigene Family; D051381:Rats; D012240:Rhodococcus / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D048229:Sulfolobus solfataricus / Q000378:metabolism; D000099252:Fatty Acid Amide Hydrolases
chemical_list: D000581:Amidohydrolases; D007210:Indoleacetic Acids; D000099252:Fatty Acid Amide Hydrolases; C015950:indoleacetamide; C019665:amidase