5.4.99.13	evolution	enzyme IcmF belongs to the family of adenosylcobalamin-dependent isomerases, whose members catalyze carbon skeleton rearrangements using radical chemistry	-, 748193	
5.4.99.13	additional information	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)	-, 748200	
5.4.99.13	additional information	GDP binding by the enzyme is accompanied by favorable enthalpic and entropic changes and is unaffected by 5'-deoxyadenosylcobalamin	-, 748223	
5.4.99.13	additional information	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	-, 748193	
5.4.99.13	physiological function	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	-, 748223	
5.4.99.13	physiological function	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	-, 748193