The D-2-hydroxyacid dehydrogenase incorrectly annotated PanE is the sole reduction system for branched-chain 2-keto acids in Lactococcus lactis.

Hydroxyacid dehydrogenases of lactic acid bacteria, which catalyze the stereospecific reduction of branched-chain 2-keto acids to 2-hydroxyacids, are of interest in a variety of fields, including cheese flavor formation via amino acid catabolism. In this study, we used both targeted and random mutagenesis to identify the genes responsible for the reduction of 2-keto acids derived from amino acids in Lactococcus lactis. The gene panE, whose inactivation suppressed hydroxyisocaproate dehydrogenase activity, was cloned and overexpressed in Escherichia coli, and the recombinant His-tagged fusion protein was purified and characterized.