Literature summary for 4.2.1.157 extracted from

Knauer, S.H.; Buckel, W.; Dobbek, H.
On the ATP-dependent activation of the radical enzyme (R)-2-hydroxyisocaproyl-CoA dehydratase (2012), Biochemistry, 51, 6609-6622.

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Activating Compound

Activating Compound	Comment	Organism	Structure
activator HadI	the activator of the 2-hydroxyisocaproyl-CoA dehydratase from Clostridium difficile is a homodimeric [4Fe-4S] cluster containing ATPase which is bound in the dimer interface. The crystal structures of the Mg-ADP, Mg-ADPNP, and nucleotide-free states of the reduced activator have been solved at 1.6-3.0 A resolution. Abstraction of the nonacidic beta-proton of the 2-hydroxyacyl-CoA compounds is achieved by the reductive generation of ketyl radicals on the substrate, which is initiated by the transfer of an electron at low redox potentials. The highly energetic electron needed on the dehydratase is donated by a [4Fe-4S] cluster containing ATPase, termed activator. ATP-hydrolysis may not be necessary for electron transfer between the activator and dehydratase. The different propensities of the ATP- versus ADP-bound activator to form a complex with the dehydratase would be in agreement with electron transfer already being enabled by binding of the ATP-bound activator to the dehydratase. ATP-hydrolysis would then be needed to regenerate the ADP-bound state of the activator whose low affinity for the dehydratase would trigger complex dissociation allowing the cycle of reduction of the activator and ATP-induced complex formation between activator and dehydratase to start again	Clostridioides difficile

Organism

Organism	UniProt	Comment	Textmining
Clostridioides difficile	Q5U925	hadI, activator of 2-hydroxyisocaproyl-CoA dehydratase	-

Subunits

Subunits	Comment	Organism
homodimer	-	Clostridioides difficile

pH Optimum

pH Optimum Minimum	pH Optimum Maximum	Comment	Organism
8	-	assay at	Clostridioides difficile

General Information

General Information	Comment	Organism
metabolism	the enzyme is involved in the reductive branch of L-leucine fermentation	Clostridioides difficile

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Release 2023.1 (January 2023)