IUBMB Enzyme Nomenclature


Accepted name: isobutyryl-CoA mutase

Reaction: 2-methylpropanoyl-CoA = butanoyl-CoA

Other name(s): isobutyryl coenzyme A mutase; butyryl-CoA:isobutyryl-CoA mutase

Systematic name: 2-methylpropanoyl-CoA CoA-carbonylmutase

Comments: 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, 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.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 116405-23-3


1. Brendelberger, G., Rétey, J., Ashworth, D.M., Reynolds, K., Willenbrock, F. and Robinson, J.A. The enzymic interconversion of isobutyryl and N-butyrylcarba(dethia)-coenzyme-A - a coenzyme-B12-dependent carbon skeleton rearrangement. Angew. Chem. Int. Ed. Engl. 27 (1988) 1089-1091.

2. Ratnatilleke, A., Vrijbloed, J.W. and Robinson, J.A. Cloning and sequencing of the coenzyme B12-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 (1999) 31679–31685. [PMID: 10531377]

3. Cracan, V., Padovani, D. and Banerjee, R. IcmF is a fusion between the radical B12 enzyme isobutyryl-CoA mutase and its G-protein chaperone. J. Biol. Chem. 285 (2010) 655–666. [PMID: 19864421]

4. Cracan, V. and Banerjee, R. Novel coenzyme B12-dependent interconversion of isovaleryl-CoA and pivalyl-CoA. J. Biol. Chem. 287 (2012) 3723–3732. [PMID: 22167181]

5. Jost, M., Born, D.A., Cracan, V., Banerjee, R. and Drennan, C.L. Structural basis for substrate specificity in adenosylcobalamin-dependent isobutyryl-CoA mutase and related acyl-CoA mutases. J. Biol. Chem. 290 (2015) 26882–26898. [PMID: 26318610]

6. Li, Z., Kitanishi, K., Twahir, U.T., Cracan, V., Chapman, D., Warncke, K. and Banerjee, R. Cofactor editing by the G-protein metallochaperone domain regulates the radical B12 enzyme IcmF. J. Biol. Chem. 292 (2017) 3977–3987. [PMID: 28130442]

[EC created 1992]

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