Structure and epimerase activity of anthocyanidin reductase from Vitis vinifera

Acta Crystallogr D Biol Crystallogr. 2009 Sep;65(Pt 9):989-1000. doi: 10.1107/S0907444909025013. Epub 2009 Aug 14.


Together with leucoanthocyanidin reductase, anthocyanidin reductase (ANR) is one of the two enzymes of the flavonoid-biosynthesis pathway that produces the flavan-3-ol monomers required for the formation of proanthocyanidins or condensed tannins. It has been shown to catalyse the double reduction of anthocyanidins to form 2R,3R-flavan-3-ols, which can be further transformed to the 2S,3R isomers by non-enzymatic epimerization. ANR from grape (Vitis vinifera) was expressed in Escherichia coli and purified. Unexpectedly, RP-HPLC, LC-MS and NMR experiments clearly established that the enzyme produces a 50:50 mixture of 2,3-cis and 2,3-trans flavan-3-ols which have been identified by chiral chromatography to be 2S,3S- and 2S,3R-flavan-3-ols, i.e. the naturally rare (+)-epicatechin and (-)-catechin, when cyanidin is used as the substrate of the reaction. The first three-dimensional structure of ANR is described at a resolution of 2.2 A and explains the inactivity of the enzyme in the presence of high salt concentrations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allosteric Regulation*
  • Anthocyanins / metabolism*
  • Crystallization
  • Crystallography, X-Ray
  • Escherichia coli / genetics
  • Isomerism
  • NADH, NADPH Oxidoreductases / chemistry*
  • NADH, NADPH Oxidoreductases / genetics
  • Oxidation-Reduction
  • Protein Conformation
  • Racemases and Epimerases / chemistry*
  • Racemases and Epimerases / genetics
  • Structure-Activity Relationship
  • Transgenes / genetics
  • Vitis / enzymology


  • Anthocyanins
  • NADH, NADPH Oxidoreductases
  • Racemases and Epimerases