This bacterial enzyme utilizes 5'-deoxyadenosylcobalamin as a cofactor. Following substrate binding, the enzyme catalyses the homolytic cleavage of the cobalt-carbon bond of AdoCbl, yielding cob(II)alamin and a 5'-deoxyadenosyl radical, which initiates the the carbon skeleton rearrangement reaction by hydrogen atom abstraction from the substrate. At the end of each catalytic cycle the 5'-deoxyadenosyl radical and cob(II)alamin recombine, regenerating the resting form of the cofactor. The enzyme is prone to inactivation resulting from occassional loss of the 5'-deoxyadenosyl molecule. Inactivated enzymes are repaired by the action of EC 2.5.1.17, cob(I)yrinic acid a,c-diamide adenosyltransferase, and a G-protein chaperone, which restore cob(II)alamin (which is first reduced to cob(I)alamin by an unidentified reductase) to 5'-deoxyadenosylcobalamin and load it back on the mutase. Some mutases are fused with their G-protein chaperone. These enzyme can also catalyse the interconversion of isovaleryl-CoA with pivalyl-CoA.
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SYSTEMATIC NAME
IUBMB Comments
2-methylpropanoyl-CoA CoA-carbonylmutase
This bacterial enzyme utilizes 5'-deoxyadenosylcobalamin as a cofactor. Following substrate binding, the enzyme catalyses the homolytic cleavage of the cobalt-carbon bond of AdoCbl, yielding cob(II)alamin and a 5'-deoxyadenosyl radical, which initiates the the carbon skeleton rearrangement reaction by hydrogen atom abstraction from the substrate. At the end of each catalytic cycle the 5'-deoxyadenosyl radical and cob(II)alamin recombine, regenerating the resting form of the cofactor. The enzyme is prone to inactivation resulting from occassional loss of the 5'-deoxyadenosyl molecule. Inactivated enzymes are repaired by the action of EC 2.5.1.17, cob(I)yrinic acid a,c-diamide adenosyltransferase, and a G-protein chaperone, which restore cob(II)alamin (which is first reduced to cob(I)alamin by an unidentified reductase) to 5'-deoxyadenosylcobalamin and load it back on the mutase. Some mutases are fused with their G-protein chaperone. These enzyme can also catalyse the interconversion of isovaleryl-CoA with pivalyl-CoA.
enzyme substrate specificity, active site architecture and determinants of substrate specificity, comparison of the substrate-bound structures to that of substrate-free holo-IcmF-GDP, overview. Acyl-CoA substrates are threaded through the TIM barrel substrate-binding domain
enzyme substrate specificity, active site architecture and determinants of substrate specificity, comparison of the substrate-bound structures to that of substrate-free holo-IcmF-GDP, overview. Acyl-CoA substrates are threaded through the TIM barrel substrate-binding domain
the GTPase activity of IcmF powers the ejection of the inactive cob(II)alamin cofactor and requires the presence of an acceptor protein, adenosyltransferase, for receiving it. Adenosyltransferase in turn converts cob(II)alamin to AdoCbl in the presence of ATP and a reductant. The repaired cofactor is then reloaded onto IcmF in a GTPase-gated step. Transfer of inactive cob(II)alamin from ATR to IcmF is disfavored. The mechanistic details of cofactor loading and offloading from the AdoCbl-dependent IcmF are distinct from those of the homologous methylmalonyl-CoA mutase/G-protein chaperone system. The nonhydrolyzable analogue, GMPPCP, weakens the affinity of IcmF for AdoCbl by about 60fold and allows loading of only one of two cofactor-binding sites. AdoCbl binding in the presence of GMPPCP is primarily enthalpically driven. The slight inhibition of AdoCbl transfer in the presence of GTP or GDP is likely due to the higher affinity of ATR for AdoCbl in the presence of these nucleotides, while ATP enhances the transfer. kinetics, overview
AdoCbl, required, the active sites in the CmIcmF dimer exhibit identical affinity for AdoCbl. Addition of isovaleryl-CoA to wild-type holo-IcmF results in formation of the intermediate cob(II)alamin. AdoCbl is quantitatively converted to cob(II)alamin when isovaleryl-CoA is added to F598A or to the F598I/L or Q742A mutants inactivating the enzyme. Cob(II)alamin formation in activates the enzyme
AdoCbl, required, two conformations: C3'-endo and C2'-endo, conformational change of the 5'-deoxyadenosyl group from C2'-endo to C3'-endo contributes to initiation of catalysis. Adenosylcobalamin (coenzyme B12) is an organometallic enzyme cofactor for radical chemistry. Its reactivity is based on a unique covalent cobalt-carbon (Co-C) bond that is sufficiently weak to allow for reversible homolytic cleavage in enzyme active sites, generating a 5'-deoxyadenosyl radical in the presence of an appropriate substrate. The radical can then abstract a substrate hydrogen atom and initiate difficult chemical transformations
the presence of GDP decreases kcat about 1.6-1.7fold while increasing the Km about 2fold. Consequently, the catalytic efficiency kcat/Km value of IcmF decreases 3fold in the presence of GDP
the presence of GTP decreases kcat about 1.6-1.7fold while increasing the Km about 2fold. Consequently, the catalytic efficiency kcat/Km value of IcmF decreases 4.5fold in the presence of GTP
enzyme IcmF belongs to the family of adenosylcobalamin-dependent isomerases, whose members catalyze carbon skeleton rearrangements using radical chemistry
enzyme IcmF belongs to the family of adenosylcobalamin-dependent isomerases, whose members catalyze carbon skeleton rearrangements using radical chemistry
IcmF is a 5'-deoxyadenosylcobalamin (AdoCbl)-dependent enzyme that catalyzes the carbon skeleton rearrangement of isobutyryl-CoA to butyryl-CoA. It is a bifunctional protein resulting from the fusion of a G-protein chaperone with GTPase activity and the cofactor- and substrate-binding mutase domains with isomerase activity. IcmF is prone to inactivation during catalytic turnover, thus setting up its dependence on a cofactor repair system. The GTPase activity of IcmF powers the ejection of the inactive cob(II)alamin cofactor and requires the presence of an acceptor protein, adenosyltransferase, for receiving it. Adenosyltransferase in turn converts cob(II)alamin to AdoCbl in the presence of ATP and a reductant. The repaired cofactor is then reloaded onto IcmF in a GTPase-gated step. The mechanistic details of cofactor loading and offloading from the AdoCbl-dependent IcmF are distinct from those of the homologous methylmalonyl-CoA mutase/G-protein chaperone system, overview
the isobutyryl-CoA mutase variant, IcmF, catalyzes the interconversion of isobutyryl-CoA and n-butyryl-CoA and it also catalyzes the interconversion between isovaleryl-CoA and pivalyl-CoA, albeit with low efficiency and high susceptibility to inactivation
the isobutyryl-CoA mutase variant, IcmF, catalyzes the interconversion of isobutyryl-CoA and n-butyryl-CoA and it also catalyzes the interconversion between isovaleryl-CoA and pivalyl-CoA, albeit with low efficiency and high susceptibility to inactivation
IcmF is a 5'-deoxyadenosylcobalamin (AdoCbl)-dependent enzyme that catalyzes the carbon skeleton rearrangement of isobutyryl-CoA to butyryl-CoA. It is a bifunctional protein resulting from the fusion of a G-protein chaperone with GTPase activity and the cofactor- and substrate-binding mutase domains with isomerase activity. IcmF is prone to inactivation during catalytic turnover, thus setting up its dependence on a cofactor repair system. The GTPase activity of IcmF powers the ejection of the inactive cob(II)alamin cofactor and requires the presence of an acceptor protein, adenosyltransferase, for receiving it. Adenosyltransferase in turn converts cob(II)alamin to AdoCbl in the presence of ATP and a reductant. The repaired cofactor is then reloaded onto IcmF in a GTPase-gated step. The mechanistic details of cofactor loading and offloading from the AdoCbl-dependent IcmF are distinct from those of the homologous methylmalonyl-CoA mutase/G-protein chaperone system, overview
enzyme IcmF in general is a fusion between the radical B12 enzyme isobutyryl-CoA mutase and its G-protein chaperone. IcmF from Cupriavidus metallidurans, which also contains a G-protein domain in addition to the mutase domains, with AdoCbl in the ICM active site and GDP-Mg2+ in the G-protein active site (holo-IcmF-GDP)
IcmF is a natural variant in which the small and large subunits found in ICM are fused via a middle G-protein chaperone domain, active site sequence comparisons, overview
IcmF is a natural variant in which the small and large subunits found in ICM are fused via a middle G-protein chaperone domain, active site sequence comparisons, overview
enzyme IcmF in general is a fusion between the radical B12 enzyme isobutyryl-CoA mutase and its G-protein chaperone. IcmF from Cupriavidus metallidurans, which also contains a G-protein domain in addition to the mutase domains, with AdoCbl in the ICM active site and GDP-Mg2+ in the G-protein active site (holo-IcmF-GDP)
size exclusion chromatography yields an estimated molecular mass of 135 kDa, consistent with the large subunit being a homodimer. The recombinant small subunit of PCM is purified as N-terminally His6-tagged protein and elutes with an apparent mass of 20 kDa in gel filtration, suggesting that it exists as a monomer based on the predicted mass of the polypeptide of 17.7 kDa. Gel filtration of a 1:1 mixture of the large and small subunits ofthe enzyme in presence of 5'-deoxyadenosylcobalamin, shows no evidence of complex formation, indicating weak interaction between the subunits under these conditions
IcmF is a natural variant in which the small and large subunits found in ICM are fused via a middle G-protein chaperone domain, domain structure and sequence comparisons, overview
IcmF is a natural variant in which the small and large subunits found in ICM are fused via a middle G-protein chaperone domain, domain structure and sequence comparisons, overview
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
purified enzyme in complex with four different substrates, GDP and isovaleryl-CoA, or isobutyryl-CoA or n-butytryl-CoA or pivalyl-CoA, hanging drop vapor diffusion technique, mixing of 0.001 ml of 11.7 mg/ml IcmF protein in 100 mM NaCl, 50 mM HEPES, pH 7.5, 1 mM GDP, 3 mM MgCl2, 0.3 mM AdoCbl, with 0.001 ml of reservoir solution containing 0.7-0.75 M potassium sodium tartrate, 0.2 M ammonium acetate, 0.1 M imidazole, pH 7.0-7.7, and 3% v/v ethylene glycol, and equilibration against 0.5 ml reservoir solution, 3-6 weeks, at 25°C, X-ray diffraction structure determination and analysis at 3.4-3.5 A resolution
site-directed mutagenesis, the mutation causes a 17fold increase in catalytic efficiency in pivalyl-CoA mutase activity and a concomitant about 240fold decrease in isobutyryl-CoA mutase activity compared to wild-type IcmF. The mutation of the single residue in IcmF tunes the substrate specificity to an about 4000fold increase in the specificity for the unnatural substrate. The F598A mutant is more susceptible to inactivation than wild-type IcmF
site-directed mutagenesis, the isobutyryl-CoA mutase activity of the mutant is diminished and the isovaleryl-CoA mutase activity is increased compared to wild-type
site-directed mutagenesis, the isobutyryl-CoA mutase activity of the mutant is diminished and the isovaleryl-CoA mutase activity is increased compared to wild-type
site-directed mutagenesis, the isobutyryl-CoA mutase activity of the mutant is diminished and the isovaleryl-CoA mutase activity is increased compared to wild-type
site-directed mutagenesis, the mutation causes a 17fold increase in catalytic efficiency in pivalyl-CoA mutase activity and a concomitant about 240fold decrease in isobutyryl-CoA mutase activity compared to wild-type IcmF. The mutation of the single residue in IcmF tunes the substrate specificity to an about 4000fold increase in the specificity for the unnatural substrate. The F598A mutant is more susceptible to inactivation than wild-type IcmF
site-directed mutagenesis, the isobutyryl-CoA mutase activity of the mutant is diminished and the isovaleryl-CoA mutase activity is increased compared to wild-type
AdoCbl is quantitatively converted to cob(II)alamin when isovaleryl-CoA is added to F598A or to the F598I/L or Q742A mutants inactivating the enzyme, The F598A mutant inactivates 3fold more rapidly than wild-type IcmF
engineering of enzyme IcmF to increase pivalyl-CoA mutase activityby targeting two active site residues predicted to be key to substrate selectivity based on sequence alignments and crystal structures. PCM-F is an artificially engineered variant of PCM (IcmF) in which the large and small subunits are fused via an 11-amino acid linker
AdoCbl is quantitatively converted to cob(II)alamin when isovaleryl-CoA is added to F598A or to the F598I/L or Q742A mutants inactivating the enzyme, The F598A mutant inactivates 3fold more rapidly than wild-type IcmF
engineering of enzyme IcmF to increase pivalyl-CoA mutase activityby targeting two active site residues predicted to be key to substrate selectivity based on sequence alignments and crystal structures. PCM-F is an artificially engineered variant of PCM (IcmF) in which the large and small subunits are fused via an 11-amino acid linker
the production of isobutanol, a branched-chain alcohol that can be used as a gasoline substitute, using a CoA-dependent pathway in recombinant Ralstonia eutropha strain H16. The designed pathway is constituted of three modules: chain elongation, rearrangement, and modification. First, the chain elongation and modification modules are integrated and optimized, esulting in the production of about 200 mg/l n-butanol from fructose or 30 mg/L from formate by engineered Ralstonia eutropha. Subsequently, the rearrangement module is incorporated, featuring native isobutyryl-CoA mutase in Ralstonia eutropha. The engineered strain produces about 30 mg/l isobutanol from fructose. The demonstrated carbon skeleton rearrangement chemistry may be used to expand the range of the chemicals accessible with CoA-dependent pathways
recombinant His-MBP-tagged wild-type enzyme and His6-SUMO-tagged mutant enzyme from Escherichia coli strain BL21(DE3) by nickel affinity chromatography, dialysis, tag cleavage by TEV protease, dialysis, amylose affinity chromatography (only wild-type), and gel filtration
IcmA, expression in Escherichia coli and Streptomyces lividans, IcmA shows 70% of homology to the methylmalonyl-CoA mutase large subunit from Streptomyces cinnamonensis
the production of isobutanol, a branched-chain alcohol that can be used as a gasoline substitute, using a CoA-dependent pathway in recombinant Ralstonia eutropha strain H16. The designed pathway involves isobutyryl-CoA mutase activity. The engineered strain produces about 30 mg/l isobutanol from fructose
IcmF is potentially useful as a reagent for bioremediation of pivalic acid found in pharmaceutical wastewaters (pivalic acid esters are used as pro-drugs) and/or for the biosynthesis of a simple beta-nonfunctional alpha-quaternary carboxylic acid. Another potential application of IcmF is in metabolic engineering of pathways to produce branched C4 and C5 building blocks that can subsequently be converted to useful derivatives, for example, the corresponding isobutyl and pivalyl alcohols
the production of isobutanol, a branched-chain alcohol that can be used as a gasoline substitute, using a CoA-dependent pathway in recombinant Ralstonia eutropha strain H16. The designed pathway involves isobutyryl-CoA mutase. The engineered strain produces about 30 mg/l isobutanol from fructose. The carbon skeleton rearrangement chemistry demonstrated may be used to expand the range of the chemicals accessible with CoA-dependent pathways
IcmF is potentially useful as a reagent for bioremediation of pivalic acid found in pharmaceutical wastewaters (pivalic acid esters are used as pro-drugs) and/or for the biosynthesis of a simple beta-nonfunctional alpha-quaternary carboxylic acid. Another potential application of IcmF is in metabolic engineering of pathways to produce branched C4 and C5 building blocks that can subsequently be converted to useful derivatives, for example, the corresponding isobutyl and pivalyl alcohols
Reciprocal isomerization of butyrate and isobutyrate by the strictly anaerobic bacterium strain WoG13 and methanogenic isobutyrate degradation by a defined triculture
Cloning and sequencing of the coenzyme B(12)-binding domain of isobutyryl-CoA mutase from Streptomyces cinnamonensis, reconstitution of mutase activity, and characterization of the recombinant enzyme produced in Escherichia coli
J. Biol. Chem.
274
31679-31685
1999
Streptomyces virginiae (Q9RJ84), Streptomyces virginiae A3823.5 (Q9RJ84)
Cloning, sequencing, expression, and insertional inactivation of the gene for the large subunit of the coenzyme B12-dependent isobutyryl-CoA mutase from Streptomyces cinnamonensis