The Enzyme Database

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Accepted name: homoaconitate hydratase
Reaction: (1R,2S)-1-hydroxybutane-1,2,4-tricarboxylate = (Z)-but-1-ene-1,2,4-tricarboxylate + H2O
For diagram of l-lysine synthesis, 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
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 (R)-homocitrate by hydration of cis-homoaconitate. The enzyme responsible for the conversion of cis-homoaconitate into (R)-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, 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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