title: Structure of the branched-chain keto acid decarboxylase (KdcA) from Lactococcus lactis provides insights into the structural basis for the chemoselective and enantioselective carboligation reaction.
abstract: The thiamin diphosphate (ThDP) dependent branched-chain keto acid decarboxylase (KdcA) from Lactococcus lactis catalyzes the decarboxylation of 3-methyl-2-oxobutanoic acid to 3-methylpropanal (isobutyraldehyde) and CO2. The enzyme is also able to catalyze carboligation reactions with an exceptionally broad substrate range, a feature that makes KdcA a potentially valuable biocatalyst for C-C bond formation, in particular for the enzymatic synthesis of diversely substituted 2-hydroxyketones with high enantioselectivity. The crystal structures of recombinant holo-KdcA and of a complex with an inhibitory ThDP analogue mimicking a reaction intermediate have been determined to resolutions of 1.6 and 1.8 A, respectively. KdcA shows the fold and cofactor-protein interactions typical of thiamin-dependent enzymes. In contrast to the tetrameric assembly displayed by most other ThDP-dependent decarboxylases of known structure, KdcA is a homodimer. The crystal structures provide insights into the structural basis of substrate selectivity and stereoselectivity of the enzyme and thus are suitable as a framework for the redesign of the substrate profile in carboligation reactions.
authors: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-17177 Stockholm, Sweden.
authors: Catrine L
authors: CL
authors: Berthold
authors: Dörte
authors: D
authors: Gocke
authors: Martin D
authors: MD
authors: Wood
authors: Finian J
authors: FJ
authors: Leeper
authors: Martina
authors: M
authors: Pohl
authors: Gunter
authors: G
authors: Schneider
mesh_terms: D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide) / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics; D020035:Holoenzymes / Q000737:chemistry* / Q000378:metabolism; D013294:Lactococcus lactis / Q000201:enzymology* / Q000235:genetics; D008956:Models, Chemical; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000235:genetics; D013237:Stereoisomerism; D013379:Substrate Specificity; D013835:Thiamine Pyrophosphate / Q000378:metabolism
chemical_list: D020035:Holoenzymes; D011994:Recombinant Proteins; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D013835:Thiamine Pyrophosphate