Bacterial Acyl-CoA Mutase Specifically Catalyzes Coenzyme B12-dependent Isomerization of 2-Hydroxyisobutyryl-CoA and (S)-3-Hydroxybutyryl-CoA

• Published in: The Journal of biological chemistry Vol. 287; no. 19; pp. 15502 - 15511
• Main Authors: Yaneva, Nadya, Schuster, Judith, Schäfer, Franziska, Lede, Vera, Przybylski, Denise, Paproth, Torsten, Harms, Hauke, Müller, Roland H., Rohwerder, Thore
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2012; American Society for Biochemistry and Molecular Biology
• Subjects: 2-Hydroxyisobutyric Acid; 3-Hydroxybutyric Acid; Acyl Coenzyme A - metabolism; Acyl-CoA Mutases; Adenosylcobalamin; Amino Acid Sequence; Bacterial Metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Betaproteobacteria - enzymology; Betaproteobacteria - genetics; Biocatalysis; Catalytic Domain; Electrophoresis, Polyacrylamide Gel; Enzyme Catalysis; Enzyme Kinetics; Enzyme Mechanisms; Enzymology; Hydrogen-Ion Concentration; Hydroxybutyrates - chemistry; Hydroxybutyrates - metabolism; Intramolecular Transferases - genetics; Intramolecular Transferases - metabolism; Isoleucine - genetics; Isoleucine - metabolism; Isomerism; Kinetics; Metalloenzymes; Molecular Sequence Data; Mutation; Protein Subunits - genetics; Protein Subunits - metabolism; Sequence Homology, Amino Acid; Spectrometry, Mass, Electrospray Ionization; Substrate Specificity; Vitamin B 12 - metabolism; Enzyme Mechanisms; Acyl-CoA Mutases; Adenosylcobalamin; Bacterial Metabolism; Enzyme Catalysis; Substrate Specificity; Enzyme Kinetics; Metalloenzymes; 2-Hydroxyisobutyric Acid; 3-Hydroxybutyric Acid
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.314690

Coenzyme B12-dependent acyl-CoA mutases are radical enzymes catalyzing reversible carbon skeleton rearrangements in carboxylic acids. Here, we describe 2-hydroxyisobutyryl-CoA mutase (HCM) found in the bacterium Aquincola tertiaricarbonis as a novel member of the mutase family. HCM specifically catalyzes the interconversion of 2-hydroxyisobutyryl- and (S)-3-hydroxybutyryl-CoA. Like isobutyryl-CoA mutase, HCM consists of a large substrate- and a small B12-binding subunit, HcmA and HcmB, respectively. However, it is thus far the only acyl-CoA mutase showing substrate specificity for hydroxylated carboxylic acids. Complete loss of 2-hydroxyisobutyric acid degradation capacity in hcmA and hcmB knock-out mutants established the central role of HCM in A. tertiaricarbonis for degrading substrates bearing a tert-butyl moiety, such as the fuel oxygenate methyl tert-butyl ether (MTBE) and its metabolites. Sequence analysis revealed several HCM-like enzymes in other bacterial strains not related to MTBE degradation, indicating that HCM may also be involved in other pathways. In all strains, hcmA and hcmB are associated with genes encoding for a putative acyl-CoA synthetase and a MeaB-like chaperone. Activity and substrate specificity of wild-type enzyme and active site mutants HcmA I90V, I90F, and I90Y clearly demonstrated that HCM belongs to a new subfamily of B12-dependent acyl-CoA mutases. Background: Carbon skeleton rearrangements of acyl-CoA esters are catalyzed by coenzyme B12-dependent mutases. Results: A bacterial mutase specifically catalyzes the isomerization of 2-hydroxyisobutyryl- and (S)-3-hydroxybutyryl-CoA. Conclusion: Substrate affinity and enzyme activity depend strongly on the active site amino acid Ile90. Significance: This is the first characterization of an enzyme isomerizing hydroxylated short chain carboxylic acids.