An Arabidopsis mutant disrupted in valine catabolism is also compromised in peroxisomal fatty acid beta-oxidation

FEBS Lett. 2004 Jul 30;571(1-3):147-53. doi: 10.1016/j.febslet.2004.06.071.


Characterisation of the Arabidopsis dbr5 mutant, which was isolated on the basis of 2,4-dichlorophenoxybutyric acid (2,4-DB) resistance, revealed that it is disrupted in the CHY1 gene. CHY1 encodes a peroxisomal protein that is 43% identical to the mammalian beta-hydroxyisobutryl-CoA hydrolase of valine catabolism. We show that 2,4-DB resistance and the associated sucrose dependent seedling growth are due to a large activity decrease of 3-ketoacyl-CoA thiolase, which is involved in peroxisomal fatty acid beta-oxidation. (14)C-feeding studies demonstrate that dbr5 and chy1 seedlings are reduced in valine catabolism. These data support the hypothesis that CHY1 plays a key role in peroxisomal valine catabolism and that disruption of this enzyme results in accumulation of a toxic intermediate, methacrylyl-CoA, that inhibits 3-ketoacyl-CoA thiolase activity and thus blocks peroxisomal beta-oxidation. We also show that CHY1 is repressed in seedlings grown on sugars, which suggests that branched chain amino acid catabolism is transcriptionally regulated by nutritional status.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 2,4-Dichlorophenoxyacetic Acid / analogs & derivatives*
  • 2,4-Dichlorophenoxyacetic Acid / pharmacology
  • Animals
  • Arabidopsis / drug effects
  • Arabidopsis / genetics*
  • Arabidopsis / growth & development
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / metabolism
  • Base Sequence
  • Chromosome Mapping
  • Chromosomes, Plant / genetics
  • Fatty Acids / metabolism*
  • Kinetics
  • Mammals
  • Oxidation-Reduction
  • Peroxisomes / metabolism*
  • Thiolester Hydrolases / metabolism
  • Valine / metabolism*


  • Arabidopsis Proteins
  • Fatty Acids
  • 2,4-Dichlorophenoxyacetic Acid
  • Thiolester Hydrolases
  • 3-hydroxyisobutyryl-CoA hydrolase
  • Valine
  • 4-(2,4-dichlorophenoxy)butyric acid