Benzoylformate decarboxylase (BED) from Pseudomonas putida is a thiamine diphosphate-dependent (ThDP) enzyme that catalyzes the asymmetric C C bond formation to (S)-2-hydroxypropiophenone [(S)-HPP] starting from benzaldehyde and acetaldehyde. The enantioselectivity of BED was shown to be a function of temperature and substrate concentration. It can additionally be changed by site-directed mutagenesis on hot spot positions in the active site. In this article, we present the effect of hydrostatic pressure up to 250 MPa on the enantioselectivity for the recombinant wtBFD as well as for the variants BED F464I, BFD A460I, and BFD A460I-F464I. A general tendency toward lower amounts of (S)-HPP could be observed at increasing pressures. For two of these variants an increase in pressure even caused an inversion in the enantioselectivity and thus increasing enantiomeric excesses, respectively. A pressure-induced increase in enantioselectivity could therefore be observed for the first time in biocatalysis to the best of our knowledge. Furthermore, the pH is shown to be a parameter that also significantly influences the enantioselectivity of the reaction mentioned above. Biotechnol. Bioeng. 2010;106: 18-26. (C) 2009 Wiley Periodicals, Inc.