Racemic borneol is an easily accessible compound which can be synthesised from an industrial commodity, the terpenoid camphor. Pure enantiomers of borneol and its isomer, isoborneol, are fragrant constituent and therefore value added side products. Enzymes for selective terpene functionalization are therefore of particular interest. Some enzymes produce preferentially (+)-camphor from racemic borneol and (-)-camphor from racemic isoborneol, leaving (-)-borneol and (-)-isoborneol left in the mixture, leading to optically pure borneol and isoborneol, respectively. In the present work, we have performed extensive computational simulations, including empirical valence bond (EVB) simulations of the enantioselective reaction of borneol dehydrogenases (BDHs). This study was conducted in close collaboration with experimental recombinant expression and characterization of enantiospecific enzymes from the Salvia sp. genome, SsBHD1 and SsBDH2, and the comparison to other known ADHs (alcohol dehydrogenases: RoBDH1, RoBDH2, SsBDH3, TpBDH1, and TpBDH1). Computational simulations started with ancestral sequence reconstruction (ASR), generating possible ancestral sequences of the studied ADHs. These potential ancestors were appended to the set of ADHs, providing additional insight into the enantiospecificity (or the lack of it) from the set of ADHs. Due to a lack of experimental 3D structures of the investigated enzymes, homology models of the different target proteins were generated. Subsequently an automated procedure for docking the various ligands (both enantiomers of borneol, isoborneol, and norborneol) studied here into the active site of the different enzymes was used. In order to ensure that the aligned structures were a meaningful fit for the system, short MD simulations were performed to validate the stability of the docked structure.

Computational and experimental investigation of selective terpene functionalization

ACS Spring Meeting 2021

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