Structure of 1-aminocyclopropane-1-carboxylate synthase, a key enzyme in the biosynthesis of the plant hormone ethylene

J Mol Biol. 1999 Dec 3;294(3):745-56. doi: 10.1006/jmbi.1999.3255.


The 2.4 A crystal structure of the vitamin B6-dependent enzyme 1-aminocyclopropane-1-carboxylate (ACC) synthase is described. This enzyme catalyses the committed step in the biosynthesis of ethylene, a plant hormone that is responsible for the initiation of fruit ripening and for regulating many other developmental processes. ACC synthase has 15 % sequence identity with the well-studied aspartate aminotransferase, and a completely different catalytic activity yet the overall folds and the active sites are very similar. The new structure together with available biochemical data enables a comparative mechanistic analysis that largely explains the catalytic roles of the conserved and non-conserved active site residues. An external aldimine reaction intermediate (external aldimine with ACC, i.e. with the product) has been modeled. The new structure provides a basis for the rational design of inhibitors with broad agricultural applications.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Aspartate Aminotransferases / chemistry
  • Binding Sites
  • Crystallography, X-Ray
  • Dimerization
  • Drug Design
  • Enzyme Inhibitors / chemical synthesis
  • Ethylenes / biosynthesis*
  • Lyases / chemistry*
  • Lyases / metabolism*
  • Models, Molecular
  • Molecular Sequence Data
  • Plants / enzymology*
  • Protein Conformation


  • Enzyme Inhibitors
  • Ethylenes
  • ethylene
  • Aspartate Aminotransferases
  • Lyases
  • 1-aminocyclopropanecarboxylate synthase