Integrating In Silico and In vitro Approaches to Dissect the Stereoselectivity of Bacillus subtilis Lipase A toward Ketoprofen Vinyl Ester

Lipase A from Bacillus subtilis: Substrate Binding, Conformational Dynamics, and Signatures of a Lid

Protein-ligand binding studies are crucial for understanding the molecular basis of biological processes and for further advancing industrial biocatalysis and drug discovery. Using computational modeling and molecular dynamics simulations, we investigated the binding of a butyrate ester substrate to the lipase A (LipA) enzyme of Bacillus subtilis. Besides obtaining a close agreement of the binding free energy with the experimental value, the study reveals a remarkable reorganization of the catalytic triad upon substrate binding, leading to increased essential hydrogen bond populations. The investigation shows the distortion of the oxyanion hole in both the substrate-bound and unbound states of LipA and highlights the strengthening of the same in the tetrahedral intermediate complex. Principal component analysis of the unbound ensemble reveals the dominant motion in LipA to be the movement of Loop-1 (Tyr129-Arg142) between two states that cover and uncover the active site, mirroring that of a lid prevalent in several lipases. This lid-like motion of Loop-1 is also supported by its tendency to spontaneously open up at an oil-water interface. Overall, this study provides valuable insights into the impact of substrate binding on the structure, flexibility, and conformational dynamics of the LipA enzyme.

Relevance and bio-catalytic strategies for the kinetic resolution of ketoprofen towards dexketoprofen

This review presents the most relevant investigations concerning the biocatalytic kinetic resolution of racemic ketoprofen to dexketoprofen for the last 22 years. The advantages related to the administration of the dex-enantiomer in terms of human health, the so called "chiral switch" in the pharmaceutical industry and the sustainability of biotransformations have been the driving forces to develop innovative technology to obtain dexketoprofen. In particular, the kinetic resolution of racemic ketoprofen through enantiomeric esterification and hydrolysis using lipases as biocatalysts are thoroughly revised and commented upon. In this context, the biocatalysts, acyl-acceptors (alcohols), reaction conditions, conversion, enantiomeric excess, and enantiomeric ratio among others are discussed. Moreover, the investigations concerning scaling up processes in order to obtain an optically pure enantiomer of the profen are presented. Finally, some guidelines about perspectives of the technology and research opportunities are given.

Characterization, crystallization and preliminary X-ray diffraction analysis of an (S)-specific esterase (pfEstA) from Pseudomonas fluorescens KCTC 1767: enantioselectivity for potential industrial applications

The structures and reaction mechanisms of enantioselective hydrolases, which can be used in industrial applications such as biotransformations, are largely unknown. Here, the X-ray crystallographic study of a novel (S)-specific esterase (pfEstA) from Pseudomonas fluorescens KCTC 1767, which can be used in the production of (S)-ketoprofen, is described. Multiple sequence alignments with other hydrolases revealed that pfEstA contains a conserved Ser67 within the S-X-X-K motif as well as a highly conserved Tyr156. Recombinant protein containing an N-terminal His tag was expressed in Escherichia coli, purified to homogeneity and characterized using SDS-PAGE, MALDI-TOF MS and enantioselective analysis. pfEstA was crystallized using a solution consisting of 1 M sodium citrate, 0.1 M CHES pH 9.5, and X-ray diffraction data were collected to a resolution of 1.9 Å with an Rmerge of 7.9%. The crystals of pfEstA belonged to space group P2(1)2(1)2(1), with unit-cell parameters a=65.31, b=82.13, c=100.41 Å, α=β=γ=90°.