title: Ethylmalonyl-CoA mutase from Rhodobacter sphaeroides defines a new subclade of coenzyme B12-dependent acyl-CoA mutases.
abstract: Coenzyme B(12)-dependent mutases are radical enzymes that catalyze reversible carbon skeleton rearrangement reactions. Here we describe Rhodobacter sphaeroides ethylmalonyl-CoA mutase (Ecm), a novel member of the family of coenzyme B(12)-dependent acyl-CoA mutases, that operates in the recently discovered ethylmalonyl-CoA pathway for acetate assimilation. Ecm is involved in the central reaction sequence of this novel pathway and catalyzes the transformation of ethylmalonyl-CoA to methylsuccinyl-CoA in combination with a second enzyme that was further identified as promiscuous ethylmalonyl-CoA/methylmalonyl-CoA epimerase. In contrast to the epimerase, Ecm is highly specific for its substrate, ethylmalonyl-CoA, and accepts methylmalonyl-CoA only at 0.2% relative activity. Sequence analysis revealed that Ecm is distinct from (2R)-methylmalonyl-CoA mutase as well as isobutyryl-CoA mutase and defines a new subfamily of coenzyme B(12)-dependent acyl-CoA mutases. In combination with molecular modeling, two signature sequences were identified that presumably contribute to the substrate specificity of these enzymes.
authors.affiliation: Mikrobiologie, Institut für Biologie II, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, 79104 Freiburg im Breisgau, Germany.
authors.forename: Tobias J
authors.initials: TJ
authors.lastname: Erb
authors.forename: Janos
authors.initials: J
authors.lastname: Rétey
authors.forename: Georg
authors.initials: G
authors.lastname: Fuchs
authors.forename: Birgit E
authors.initials: BE
authors.lastname: Alber
mesh_terms: D000214:Acyl Coenzyme A / Q000737:chemistry*; D003001:Cloning, Molecular; D003038:Cobamides / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics; D019751:Intramolecular Transferases / Q000737:chemistry* / Q000502:physiology; D007535:Isomerases / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D008956:Models, Chemical; D010641:Phenotype; D010802:Phylogeny; D011994:Recombinant Proteins / Q000737:chemistry; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D012984:Software; D013379:Substrate Specificity; D013997:Time Factors
chemical_list: D000214:Acyl Coenzyme A; D003038:Cobamides; D011994:Recombinant Proteins; C102829:ethylmalonyl-coenzyme A; D007535:Isomerases; D019751:Intramolecular Transferases; C534388:ethylmalonyl-CoA mutase, Rhodobacter sphaeroides; C000913:cobamamide