3-Isopropylmalate dehydratase, catalytic domain (IPR033941)

Short name: IPMI_cat

Overlapping homologous superfamilies

Domain relationships


This entry represents the aconitase-like catalytic domain of 3-isopropylmalate dehydratase (IPMI) and related uncharacterized proteins.

3-isopropylmalate dehydratase (or isopropylmalate isomerase; EC: catalyses the stereo-specific isomerisation of 2-isopropylmalate and 3-isopropylmalate, via the formation of 2-isopropylmaleate. This enzyme performs the second step in the biosynthesis of leucine, and is present in most prokaryotes and many fungal species. The prokaryotic enzyme is a heterodimer composed of a large (LeuC) and small (LeuD) subunit, while the fungal form is a monomeric enzyme. Both forms of isopropylmalate are related and are part of the larger aconitase family [PMID: 9020582]. Aconitases are mostly monomeric proteins which share four domains in common and contain a single, labile [4Fe-4S] cluster. Three structural domains (1, 2 and 3) are tightly packed around the iron-sulphur cluster, while a fourth domain (4) forms a deep active-site cleft. The prokaryotic enzyme is encoded by two adjacent genes, leuC and leuD, corresponding to aconitase domains 1-3 and 4 respectively [PMID: 1400210, PMID: 9813279]. LeuC does not bind an iron-sulphur cluster. It is thought that some prokaryotic isopropylamalate dehydrogenases can also function as homoaconitase EC:, converting cis-homoaconitate to homoisocitric acid in lysine biosynthesis [PMID: 15522288]. Homoaconitase has been identified in higher fungi (mitochondria) and several archaea and one thermophilic species of bacteria, Thermus thermophilus [PMID: 16524361]. It is also found in the higher plant Arabidopsis thaliana, where it is targeted to the chloroplast [PMID: 20663849].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0003861 3-isopropylmalate dehydratase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.