The unique substrate specificity of human AOC2, a semicarbazide-sensitive amine oxidase

Cell Mol Life Sci. 2009 Aug;66(16):2743-57. doi: 10.1007/s00018-009-0076-5. Epub 2009 Jul 9.


Semicarbazide-sensitive amine oxidases (SSAOs) catalyze oxidative deamination of primary amines, but the true physiological function of these enzymes is still poorly understood. Here, we have studied the functional and structural characteristics of a human cell-surface SSAO, AOC2, which is homologous to the better characterized family member, AOC3. The preferred in vitro substrates of AOC2 were found to be 2-phenylethylamine, tryptamine and p-tyramine instead of methylamine and benzylamine, the favored substrates of AOC3. Molecular modeling suggested structural differences between AOC2 and AOC3, which provide AOC2 with the capability to use the larger monoamines as substrates. Even though AOC2 mRNA was expressed in many tissues, the only tissues with detectable AOC2-like enzyme activity were found in the eye. Characterization of AOC2 will help in evaluating the contribution of this enzyme to the pathological processes attributed to the SSAO activity and in designing specific inhibitors for the individual members of the SSAO family.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amine Oxidase (Copper-Containing) / chemistry
  • Amine Oxidase (Copper-Containing) / metabolism*
  • Amine Oxidase (Copper-Containing) / physiology
  • Cell Adhesion Molecules / chemistry
  • Cell Adhesion Molecules / metabolism
  • Cell Adhesion Molecules / physiology
  • Cloning, Molecular
  • Dimerization
  • Eye / metabolism
  • Eye Proteins / chemistry
  • Eye Proteins / metabolism*
  • Eye Proteins / physiology
  • Humans
  • Kinetics
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Oxidoreductases Acting on CH-NH Group Donors / chemistry
  • Oxidoreductases Acting on CH-NH Group Donors / metabolism*
  • Oxidoreductases Acting on CH-NH Group Donors / physiology
  • Phenethylamines / metabolism
  • Protein Structure, Tertiary
  • RNA, Messenger / metabolism
  • Substrate Specificity
  • Tryptamines / metabolism
  • Tyramine / metabolism


  • Cell Adhesion Molecules
  • Eye Proteins
  • Phenethylamines
  • RNA, Messenger
  • Tryptamines
  • phenethylamine
  • tryptamine
  • AOC2 protein, human
  • AOC3 protein, human
  • Amine Oxidase (Copper-Containing)
  • Oxidoreductases Acting on CH-NH Group Donors
  • Tyramine