Crotonase family

The crotonase family comprises mechanistically diverse proteins that share a conserved trimeric quaternary structure, the core of which consists of 4 turns of a n superhelix.
Some enzymes in the superfamily have been shown to display dehalogenase, hydratase, and isomerase activities, while others have been implicated in carbon-carbon bond formation and cleavage as well as the hydrolysis of thioesters. However, these different enzymes share the need to stabilize an enolate anion intermediate derived from an acyl-CoA substrate. This is accomplished by two structurally conserved peptidic NH groups that provide hydrogen bonds to the carbonyl moieties of the acyl-CoA substrates and form an "oxyanion hole". The CoA thioester derivatives bind in a characteristic hooked shape and a conserved tunnel binds the pantetheine group of CoA, which links the 3'-phosphate ADP binding site to the site of reaction. Enzymes in the crotonase superfamily include:

Enoyl-CoA hydratase, which catalyses the hydratation of 2-trans-enoyl-CoA into 3-hydroxyacyl-CoA.
3-2trans-enoyl-CoA isomerase, which shifts the 3-double bond of the intermediates of unsaturated fatty acid oxidation to the 2-trans position.
3-hydroxybutyryl-CoA dehydrogenase, a bacterial enzyme involved in the butyrate/butanol-producing pathway.
4-Chlorobenzoyl-CoA dehalogenase, a Pseudomonas enzyme which catalyses the conversion of 4-chlorobenzoate-CoA to 4-hydroxybenzoate-CoA.
Dienoyl-CoA isomerase, which catalyses the isomerisation of 3-trans,5-cis-dienoyl-CoA to 2-trans,4-trans-dienoyl-CoA.
Naphthoate synthase, a bacterial enzyme involved in the biosynthesis of menaquinone.
Carnitine racemase, which catalyses the reversible conversion of crotonobetaine to L-carnitine in Escherichia coli.
Methylmalonyl CoA decarboxylase, which has a hexameric structure.
Carboxymethylproline synthase, which is involved in carbapenem biosynthesis.
6-oxo camphor hydrolase, which catalyses the desymmetrization of bicyclic beta-diketones to optically active keto acids.
The alpha subunit of fatty acid oxidation complex, a multi-enzyme complex that catalyses the last three reactions in the fatty acid beta-oxidation cycle.
AUH protein, a bifunctional RNA-binding homologue of enoyl-CoA hydratase.

Human proteins containing this domain

; CDY2B; CDYL; CDYL2; DCI; ECH1; ECHDC1; ECHDC2;
ECHDC3; ECHS1; EHHADH; HADHA; HCA64; HIBCH; PECI;