IUBMB Enzyme Nomenclature


Accepted name: homoaconitate hydratase

Reaction: (1R,2S)-1-hydroxybutane-1,2,4-tricarboxylate = (Z)-but-1-ene-1,2,4-tricarboxylate + H2O

For diagram click here.

Glossary: cis-homoaconitate = (Z)-but-1-ene-1,2,4-tricarboxylate
(R)-homocitrate = (2R)-2-hydroxybutane-1,2,4-tricarboxylate
homoisocitrate = (–)-threo-homoisocitrate = (1R,2S)-1-hydroxybutane-1,2,4-tricarboxylate

homocitrate = (2R)-2-hydroxybutane-1,2,4-tricarboxylate
homoisocitrate = (1R,2S)-1-hydroxybutane-1,2,4-tricarboxylate

Other name(s): homoaconitase; cis-homoaconitase; HACN; Lys4; LysF; 2-hydroxybutane-1,2,4-tricarboxylate hydro-lyase (incorrect)

Systematic name: (1R,2S)-1-hydroxybutane-1,2,4-tricarboxylate hydro-lyase [(Z)-but-1-ene-1,2,4-tricarboxylate-forming]

Comments: Requires a [4Fe-4S] cluster for activity. The enzyme from the hyperthermophilic eubacterium Thermus thermophilus can catalyse the reaction shown above but cannot catalyse the previously described reaction, i.e. formation of homocitrate by hydration of cis-homoaconitate. The enzyme responsible for the conversion of cis-homoaconitate into homocitrate in T. thermophilus is unknown at present but the reaction can be catalysed in vitro using aconitate hydratase from pig (EC [2].

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9030-68-6


1. Strassman, M. and Ceci, L.N. Enzymatic formation of cis-homoaconitic acid, an intermediate in lysine biosynthesis in yeast. J. Biol. Chem. 241 (1966) 5401-5407. [PMID: 5954805]

2. Jia, Y., Tomita, T., Yamauchi, K., Nishiyama, M. and Palmer, D.R. Kinetics and product analysis of the reaction catalysed by recombinant homoaconitase from Thermus thermophilus. Biochem. J. 396 (2006) 479-485. [PMID: 16524361]

3. Zabriskie, T.M. and Jackson, M.D. Lysine biosynthesis and metabolism in fungi. Nat. Prod. Rep. 17 (2000) 85-97. [PMID: 10714900]

[EC created 1972, modified 2007]

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