Enantiocomplementary Enzymatic Resolution of the Chiral Auxiliary: cis,cis-6-(2,2-Dimethylpropanamido)spiro[4.4]nonan-1-ol and the Molecular Basis for the High Enantioselectivity of Subtilisin Carlsberg

Enantioselectivity of d-amino acid oxidase in the presence of ionic liquids

In this paper, enantioselectivities of d-amino acid oxidase (DAAO) in ten ionic liquids were investigated in detail.

Enantioselective Transesterification Catalysis by Nanosized Serine Protease Subtilisin Carlsberg Particles in Tetrahydrofuran

Enzyme catalysis in organic solvents is a powerful tool for stereo-selective synthesis but the enantioselectivity is still hard to predict. To overcome this obstacle, we employed a nanoparticulate formulation of subtilisin Carlsberg (SC) and designed a series of 14 structurally related racemic alcohols. They were employed in the model transesterification reaction with vinyl butyrate and the enantioselectivities were determined. In general, short alcohol side chains led to low enantioselectivties, while larger and bulky side chains caused better discrimination of the enantiomers by the enzyme. With several bulky substrates high enantioselectivities with E>100 were obtained. Computational modeling highlighted that key to high enantioselectivity is the discrimination of the R and S substrates by the sole hydrophobic binding pocket based on their size and bulkiness. While bulky S enantiomer side chains could be accommodated within the binding pocket, bulky R enantiomer side chains could not. However, when also the S enantiomer side chain becomes too large and does not fit into the binding pocket anymore, enantioselectivity accordingly drops.

Enthalpie and Entropie Contributions in the Transesterification of Sucrose: Computational Study of Lipases and Subtilisin

Transesterification of sucrose with fatty acids catalyzed by subtilisin Carlsberg occurs with regioselectivity that is different from that in lipases. Thermomyces lanuginosus lipase (TlL) and Candida antarctica lipase B (CALB) catalyze synthesis at positions 6 and 6', with differing abilities, while subtilisin catalysis leads to the 1'-acylated sucrose. The catalytic machinery in lipases is approximately mirrored in subtilisins but different pocket morphologies including size, shape, and rearrangement of the catalytic elements underlies the differing regioselectivities. The thermodynamic consequences of these differences on the above reactions have been explored systematically using computational methods, determining the free energies of interaction of the putative transition-state adducts. Analysis of the conformers with the lowest transition state energies (protein-ligand interactions and vibrational entropy contributions) indicates that enthalpic factors control specificities in lipases while entropic factors are more important in subtilisin.