EC - Methanogen homoaconitase

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IntEnz Enzyme Nomenclature


Accepted name:
methanogen homoaconitase
Other name:
methanogen HACN
Systematic name:
(R)-2-hydroxybutane-1,2,4-tricarboxylate hydro-lyase [(1R,2S)-1-hydroxybutane-1,2,4-tricarboxylate-forming]




This enzyme catalyses several reactions in the pathway of coenzyme-B biosynthesis in methanogenic Archaea. Requires a [4Fe-4S] cluster for activity. In contrast to EC, homoaconitate hydratase, this enzyme can catalyse both the dehydration of (R)-homocitrate to form cis-homoaconitate and the subsequent hydration reaction that forms homoisocitrate. In addition to cis-homoaconitate, the enzyme can also catalyse the hydration of the physiological substrates dihomocitrate and trihomocitrate as well as the non-physiological substrate tetrahomocitrate. cis-Aconitate and threo-DL-isocitrate cannot act as substrates, and (S)-homocitrate and trans-homoaconitate act as inhibitors of the enzyme.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Protein domains and families: PROSITE:PDOC00423
Structural data: CSA , EC2PDB


  1. Drevland, R. M., Jia, Y., Palmer, D.R.J. and Graham, D.E.
    Methanogen homoaconitase catalyzes both hydrolyase reactions in coenzyme B biosynthesis.
    J. Biol. Chem. 283 : 28888-28896 (2008). [PMID: 18765671]

[EC created 2009]