An evaluation of the substrate specificity and asymmetric synthesis potential of the cloned L-lactate dehydrogenase from Bacillusstearothermophilus

Abstract

The potential utility of the L-lactate dehydrogenase of Bacillusstearothermophilus (BSLDH) for stereospecific, preparative-scale reductions of α-keto acids to (S)-α-hydroxy acids of > 99% ee has been demonstrated. BSLDH is a stable, thermophilic, enzyme whose gene has been cloned into a high-expression vector to assure its plentiful supply. Its specificity for keto acid substrates possessing straight- and branched-chain alkyl, cyclopropyl, or phenyl groups has been evaluated in preparative and kinetic terms, and compared with that of the mammalian pig heart enzyme (PHLDH). The specificities of BSLDH and PHLDH are similar, with branched alkyl-chain keto acids being poor substrates for both enzymes. Keywords: enzymes in organic syntheses, lactate dehydrogenase, asymmetric synthesis.