Arabidopsis amidase 1, a member of the amidase signature family

FEBS J. 2007 Jul;274(13):3440-51. doi: 10.1111/j.1742-4658.2007.05876.x. Epub 2007 Jun 6.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amidohydrolases / chemistry*
  • Amino Acid Sequence
  • Animals
  • Arabidopsis / genetics*
  • Arabidopsis / physiology*
  • Catalytic Domain
  • Conserved Sequence
  • Indoleacetic Acids / chemistry
  • Models, Biological
  • Molecular Sequence Data
  • Multigene Family
  • Rats
  • Rhodococcus / metabolism
  • Sequence Homology, Amino Acid
  • Sulfolobus solfataricus / metabolism


  • Indoleacetic Acids
  • indoleacetamide
  • Amidohydrolases
  • fatty-acid amide hydrolase
  • amidase