Propioin Synthesis Using Thiamine Diphosphate-Dependent Enzymes

摘要

Benzaldehyde lyase(BAL,EC 4.1.238)from Pseudomonas fluorescens and benzoylfor-mate decarboxylase(BFD,EC 4.1.1.7)from Pseudomonas putida are thiamine diphosphate-dependent enzymes.These enzymes share a common tetrameric structure and catalyze various C-C-bond forming and breaking reactions.Here we describe a detailed study of the asymmetric synthesis of propioin from propanal catalyzed by BAL or BFD in aqueous solution in a batch reactor.Both enzymes are deactivated in the presence of high concentration of propanal.Compared to BAL,BFD is more stable under reaction conditions as well as during storage.The kinetic studies showed a typical Michaelis-Menten kinetic for BAL with a maximal specific reaction rate of 26.2 U/mg and an unusually high K_M of 415 mM,whereas the vl[S]-plot for BFD is almost linear in the concentration range(100-1500 mM)investigated.Both enzymes produce propioin with opposite enantiomeric excess:BAL produced the(S)-propioin(ee of 35%),whereas BFD yielded the(R)-enantiomer(ee of 67%).