Synthesis of enantiomerically puretrans-(1R,2R)- andcis-(1S,2R)-1-amino-2-indanol by lipase and ω-transaminase

Computational Prediction of ω-Transaminase Specificity by a Combination of Docking and Molecular Dynamics Simulations

ω-Transaminases (ω-TAs) catalyze the conversion of ketones to chiral amines, often with high enantioselectivity and specificity, which makes them attractive for industrial production of chiral amines. Tailoring ω-TAs to accept non-natural substrates is necessary because of their limited substrate range. We present a computational protocol for predicting the enantioselectivity and catalytic selectivity of an ω-TA from Vibrio fluvialis with different substrates and benchmark it against 62 compounds gathered from the literature. Rosetta-generated complexes containing an external aldimine intermediate of the transamination reaction are used as starting conformations for multiple short independent molecular dynamics (MD) simulations. The combination of molecular docking and MD simulations ensures sufficient and accurate sampling of the relevant conformational space. Based on the frequency of near-attack conformations observed during the MD trajectories, enantioselectivities can be quantitatively predicted. The predicted enantioselectivities are in agreement with a benchmark dataset of experimentally determined ee% values. The substrate-range predictions can be based on the docking score of the external aldimine intermediate. The low computational cost required to run the presented framework makes it feasible for use in enzyme design to screen thousands of enzyme variants.

Biocatalytic routes to anti-viral agents and their synthetic intermediates

An assessment of biocatalytic strategies for the synthesis of anti-viral agents, offering guidelines for the development of sustainable production methods for a future COVID-19 remedy.

Improving Catalytic Efficiency and Changing Substrate Spectrum for Asymmetric Biocatalytic Reductive Amination

With the advantages of biocatalytic method, enzymes have been excavated for the synthesis of chiral amino acids by the reductive amination of ketones, offering a promising way of producing pharmaceutical intermediates. In this work, a robust phenylalanine dehydrogenase (PheDH) with wide substrate spectrum and high catalytic efficiency was constructed through rational design and active-site-targeted, site-specific mutagenesis by using the parent enzyme from Bacillus halodurans. Active sites with bonding substrate and amino acid residues surrounding the substrate binding pocket, 49L-50G-51G, 74M,77K, 122G-123T-124D-125M, 275N, 305L and 308V of the PheDH, were identified. Noticeably, the new mutant PheDH (E113D-N276L) showed approximately 6.06-fold increment of k_cat/Km in the oxidative deamination and more than 1.58-fold in the reductive amination compared to that of the wide type. Meanwhile, the PheDHs exhibit high capacity of accepting benzylic and aliphatic ketone substrates. The broad specificity, high catalytic efficiency and selectivity, along with excellent thermal stability, render these broad-spectrum enzymes ideal targets for further development with potential diagnostic reagent and pharmaceutical compounds applications.

Biocatalytic approaches towards the stereoselective synthesis of vicinal amino alcohols

The global need for clean manufacturing technologies and the management of hazardous chemicals and waste present new research challenges to both chemistry and biotechnology.

Asymmetric Preparation of prim-, sec-, and tert-Amines Employing Selected Biocatalysts

This account focuses on the application of ω-transaminases, lyases, and oxidases for the preparation of amines considering mainly work from our own lab. Examples are given to access α-chiral primary amines from the corresponding ketones as well as terminal amines from primary alcohols via a two-step biocascade. 2,6-Disubstituted piperidines, as examples for secondary amines, are prepared by biocatalytical regioselective asymmetric monoamination of designated diketones followed by spontaneous ring closure and a subsequent diastereoselective reduction step. Optically pure tert-amines such as berbines and N-methyl benzylisoquinolines are obtained by kinetic resolution via an enantioselective aerobic oxidative C-C bond formation.

omega-Transaminases for the synthesis of non-racemic alpha-chiral primary amines

Optically pure amines are highly valuable products or key intermediates for a vast number of bioactive compounds; however, efficient methods for their preparation are rare. omega-Transaminases (TAs) can be applied either for the kinetic resolution of racemic amines or for the asymmetric synthesis of amines from the corresponding ketones. The latter process is more advantageous because it leads to 100% product, and is therefore a major focus of this review. This review summarizes various methodologies for transamination reactions, and provides an overview of omega-TAs that have the potential to be used for the preparation of a broad spectrum of alpha-chiral amines. Recent methodological developments as well as some recently identified novel omega-TAs warrant an update on this topic.

An amine: hydroxyacetone aminotransferase from Moraxella lacunata WZ34 for alaninol synthesis

An amine:hydroxyacetone aminotransferase from an isolated soil bacterium, Moraxella lacunata WZ34, was employed to synthesize alaninol in the presence of hydroxyacetone and isopropylamine in this study. The optimal carbon and nitrogen sources were glycerol and beef extract, respectively. A wide range of amino donor specificity was detected with the aminotransferase, which exhibited a relative high activity (9.83 U mL(-1)) in the presence of isopropylamine. The enzyme was the most active at pH 8.5, and showed relatively higher activity at alkaline than acidic pH. Maximum activity was achieved at 30 degrees C, and the enzyme had good thermal stability below 60 degrees C. Metal ions such as Mg(2+) had positive effect (132.6%) on the enzyme, and (aminooxy)acetic acid, a typical aminotransferase inhibitor, significantly inhibited its activity. The enzyme activity was enhanced by the addition of 0.05 mM pyridoxal-5'-phosphate (PLP).

Conformations of 2-aminoindan in a supersonic jet: the role of intramolecular N-H...pi hydrogen bonding

Laser-induced fluorescence (LIF), dispersed fluorescence (DF), mass-resolved one-color resonance enhanced two-photon ionization (RE2PI) and UV-UV hole-burning spectra of 2-aminoindan (2-AI) were measured in a supersonic jet. The hole-burning spectra demonstrated that the congested vibronic structures observed in the LIF excitation spectrum were responsible for three conformers of 2-AI. The origins of the conformers were observed at 36931, 36934, and 36955 cm(-1). The DF spectra obtained by exciting the band origins of the three conformers showed quite similar vibrational structures, with the exception of the bands around 600-900 cm(-1). The molecular structures of the three conformers were assigned with the aid of ab initio calculations at the MP2/6-311+G(d,p) level. An amino hydrogen of the most stable conformer points toward the benzene ring. The stability of the most stable conformer was attributed to an intramolecular N-H...pi hydrogen bonding between the hydrogen atom and the pi-electron of the benzene ring. The other two conformers, devoid of intramolecular hydrogen bonding, were also identified for 2-AI. This suggests weak hydrogen bonding in the most stable conformer. The intramolecular N-H...pi hydrogen bonding in 2-AI was discussed in comparison with other weak hydrogen-bonding systems.

One-pot synthesis of amino-alcohols using a de-novo transketolase and β-alanine: Pyruvate transaminase pathway inEscherichia coli

Biocatalysis continues to emerge as a powerful technique for the efficient synthesis of optically pure pharmaceuticals that are difficult to access via conventional chemistry. The power of biocatalysis can be enhanced if two or more reactions can be achieved by a single whole cell biocatalyst containing a pathway designed de-novo to facilitate a required synthetic sequence. The enzymes transketolase (TK) and transaminase (TAm) respectively catalyze asymmetric carbon--carbon bond formation and amine group addition to suitable substrate molecules. The ability of a transaminase to accept the product of the transketolase reaction can allow the two catalysts to be employed in series to create chiral amino-alcohols from achiral substrates. As proof of principle, the beta-alanine: pyruvate aminotransferase (beta-A:P TAm) from Pseudomonas aeruginosa has been cloned, to create plasmid pQR428, for overexpression in E.coli strain BL21gold(DE3). Production of the beta-A:P TAm alongside the native transketolase (overexpressed from plasmid pQR411), in a single E.coli host, has created a novel biocatalyst capable of the synthesis of chiral amino alcohols via a synthetic two-step pathway. The feasibility of using the biocatalyst has been demonstrated by the formation of a single diastereoisomer of 2-amino-1,3,4-butanetriol (ABT) product, in up to 21% mol/mol yield, by the beta-A:P TAm, via transamination of L-erythrulose synthesized by TK, from achiral substrates glycolaldehyde (GA) and beta-hydroxypyruvate (beta-HPA). ABT synthesis was achieved in a one-pot process, using either whole cells of the dual plasmid strain or cell lysate, while the dual alcohol-amine functionality of ABT makes it an excellent synthon for many pharmaceutical syntheses.