Dihydroxy-acid dehydratase

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dihydroxy-acid dehydratase
EC no.
CAS no.9024-32-2
IntEnzIntEnz view
ExPASyNiceZyme view
MetaCycmetabolic pathway
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

In enzymology, a dihydroxy-acid dehydratase (EC is an enzyme that catalyzes the chemical reaction

2,3-dihydroxy-3-methylbutanoate 3-methyl-2-oxobutanoate + H2O

Hence, this enzyme has one substrate, 2,3-dihydroxy-3-methylbutanoate, and two products, 3-methyl-2-oxobutanoate (α-ketoisovaleric acid) and H2O.

This enzyme participates in valine, leucine and isoleucine biosynthesis and pantothenate and coenzyme A (CoA) biosynthesis.


This enzyme belongs to the family of lyases, specifically the hydro-lyases, which cleave carbon-oxygen bonds. The systematic name of this enzyme class is 2,3-dihydroxy-3-methylbutanoate hydro-lyase (3-methyl-2-oxobutanoate-forming). Other names in common use include

  • acetohydroxyacid dehydratase,
  • alpha,beta-dihydroxyacid dehydratase,
  • 2,3-dihydroxyisovalerate dehydratase,
  • alpha,beta-dihydroxyisovalerate dehydratase,
  • dihydroxy acid dehydrase,
  • DHAD,
  • and 2,3-dihydroxy-acid hydro-lyase.


Further reading[edit]

  • Kanamori M, Wixom RL (Mar 1963). "Studies in valine biosynthesis. V. Characteristics of the purified dihydroxyacid dehydratase from spinach leaves". The Journal of Biological Chemistry. 238: 998–1005. PMID 13962154.
  • Myers JW (May 1961). "Dihydroxy acid dehydrase: an enzyme involved in the biosynthesis of isoleucine and valine". The Journal of Biological Chemistry. 236: 1414–8. PMID 13727223.