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
Acta Crystallographica Section D
Volume 63, Issue 12, pages 1217–1224, December 2007
How to Cite
Berthold, C. L., Gocke, D., Wood, M. D., Leeper, F. J., Pohl, M. and Schneider, G. (2007), 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. Acta Crystallographica D, 63: 1217–1224. doi: 10.1107/S0907444907050433
- thiamin diphosphate;
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 Å, 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.