| 1. |
- Kazemi, Masoud, et al.
(författare)
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Computational Study of Mycobacterium smegmatis Acyl Transferase Reaction Mechanism and Specificity
- 2018
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 8:11, s. 10698-10706
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Tidskriftsartikel (refereegranskat)abstract
- The acyl transferase from Mycobacterium smegmatis (MsAcT) catalyzes the acyl transfer between a range of primary and secondary alcohols, whereby its outstanding ability is to perform this reaction in aqueous solution. Therefore, MsAcT opens different options for acylation reactions enabling alternatives for many conventionally hydrolytic enzymes used in biocatalysis. Nevertheless, hydrolysis is still a major side reaction of this enzyme. To provide a detailed understanding of the competition between hydrolysis and transesterification reactions, a combination of density functional theory and free energy perturbation methods have been employed. The relative binding free energies and the energy profiles of the chemical steps involved in the reaction were calculated for a number of substrates. The calculations show that the enzyme active site exhibits a higher affinity for substrates with an aromatic ring. The rate-determining step corresponds to the collapse of a negatively charged tetrahedral intermediate in the substrate acylation half-reaction. The intrinsic barriers of the transesterification and hydrolysis half-reactions are calculated to be of similar heights, suggesting that the determining factor in the MsAcT specificity is the higher binding affinity of the active site for the alcohol substrates relative to water. Finally, the influence of the acyl donor on the MsAcT-catalyzed reaction is also investigated by considering different esters in the calculations.
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| 2. |
- Marx, Lisa, et al.
(författare)
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Chemoenzymatic Approaches to the Synthesis of the Calcimimetic Agent Cinacalcet Employing Transaminases and Ketoreductases
- 2018
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Ingår i: Advanced Synthesis and Catalysis. - : Wiley-VCH Verlagsgesellschaft. - 1615-4150 .- 1615-4169. ; 360:11, s. 2157-2165
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Several chemoenzymatic routes have been explored for the preparation of cinacalcet, a calcimimetic agent. Transaminases (TAs) and ketoreductases (KREDs) turned out to be useful biocatalysts for the preparation of key optically active precursors. Thus, the asymmetric amination of 1â€acetonaphthone yielded an enantiopure (R)â€amine, which can be alkylated in one step to yield cinacalcet. Alternatively, the bioreduction of the same ketone resulted in an enantiopure (S)â€alcohol, which was easily converted into the previous (R)â€amine. In addition, the reduction was efficiently performed with the KRED and its cofactor coâ€immobilized on the same porous surface. This selfâ€sufficient heterogeneous biocatalyst presented an accumulated total turnover number (TTN) for the cofactor of 675 after 5 consecutive operational cycles. Finally, in a preparative scale synthesis the TAâ€based approach was performed in aqueous medium and led to enantiopure cinacalcet in two steps and 50% overall yield.
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