Reaction Equilibrium of the ω-Transamination of (S)-Phenylethylamine: Experiments and ePC-SAFT Modeling

Crystallization-based downstream processing of ω-transaminase- and amine dehydrogenase-catalyzed reactions

This study highlights the use of selective crystallization as a downstream-processing concept for amine products from biocatalytic reactions.

High-Pressure-Mediated Thiourea-Organocatalyzed Asymmetric Michael Addition to (Hetero)aromatic Nitroolefins: Prediction of Reaction Parameters by PCP-SAFT Modelling

Thiourea-organocatalyzed Michael additions of diethyl malonate to various heteroaromatic nitroolefins (13 examples) have been studied under high-pressure (up to 800 MPa) and ambient pressure conditions. High pressure was conducive to enhanced product yields by a factor of 2-12 at a given reaction time, high reaction rates (reaction times were decreased from 72-24 h down to 4-24 h) and high enantioselectivity. Elucidating the effects of solvents for maximizing reaction rates and yields has been carried out using the Perturbed-Chain Polar Statistical Associating Fluid Theory (PCP-SAFT), allowing for the first time a prediction of the kinetic profiles under high-hydrostatic-pressure conditions.

Standard Gibbs energy of metabolic reactions: IV. Triosephosphate isomerase reaction

The glycolytic pathway is present in most organisms and represents a central part of the energy production mechanism in a cell. For a general understanding of glycolysis, the investigation from a thermodynamic point of view is essential and allows realising thermodynamic feasibility analyses under in vivo conditions. However, available literature standard Gibbs energies of reaction, Δ^Rg'⁰, are calculated using equilibrium-molality ratios K_m', which might lead to a misinterpretation of the glycolytic pathway. It was the aim of this work to thermodynamically investigate the triosephosphate isomerase (TPI) reaction to provide new activity-based reaction data. In vitro equilibrium experiments were performed, and activity coefficients were predicted with the equation of state electrolyte PC-SAFT (ePC-SAFT). The combination of experimental concentrations and predicted activity coefficients yielded the thermodynamic equilibrium constant K_a and a new value for Δ^Rg'⁰(298.15 K, pH 7) = 7.1 ± 0.3 kJ mol^‑1. The availability of the new Δ^Rg'⁰ value allowed predicting influences of the reaction medium on the reaction equilibrium of the TPI reaction. In this work, influences of the initial substrate concentration, pH and Mg²⁺ concentration on the reaction equilibrium were investigated and a method is presented to predict these influences. The higher the substrate concentration and the higher the temperature, the stronger the reaction equilibrium is shifted on the product side. While the pH did not have a significant influence on the reaction equilibrium, Mg²⁺ yielded a shift of the reaction equilibrium to the substrate side. All these effects were predicted correctly with ePC-SAFT. Based on the ePC-SAFT predictions we concluded that a charge-reduction of the product by complexation of the product with Mg²⁺ was responsible for the strong influence of Mg²⁺ on the reaction equilibrium. Finally, the standard enthalpy of reaction of Δ^Rh^'0(pH 7) = 18 ± 7 kJ mol^‑1 was determined with the equilibrium constants K_a at 298.15 K, 304.15 K and 310.15 K using the van 't Hoff equation.

Odd–even effect for efficient bioreactions of chiral alcohols and boosted stability of the enzyme

We describe a holistic approach for achieving a nearly quantitative conversion for an enzymatic reaction while simultaneously increasing the long-term stability of the enzyme. The approach provided chemical control of bioreactions by utilizing newly synthesized tetrahydrothiophene-based ionic liquids (THT ILs). We showcased its power by using THT-ILs as additives at a low concentration (only 10 mmol L⁻¹) in the alcohol dehydrogenase (ADH)-catalyzed synthesis of methylated 1-phenylethanol (Me-PE). We discovered an “odd–even” effect of the IL-cation chain length: Me-PE displayed beneficial interactions with THT ILs having odd-numbered chain lengths and deleterious interactions with those having even-numbered chain lengths. An intermolecular thermodynamic simulation of the bulk phase and critical micelle concentration investigations of the local surroundings of the THT-ILs proved the occurrence of these interactions, and these two methods confirmed the odd–even effect from different perspectives. Additionally, storing the ADH enzyme in pure THT IL at room temperature allowed for a boosted long-term stability of the enzyme (500 times greater than that in aqueous buffer) without the need for freezing.

We describe a holistic approach for achieving a nearly quantitative conversion for an enzymatic reaction while simultaneously increasing the long-term stability of the enzyme.

Application of ω-Transaminases in the Pharmaceutical Industry

Chiral amines are valuable building blocks for the pharmaceutical industry. ω-TAms have emerged as an exciting option for their synthesis, offering a potential "green alternative" to overcome the drawbacks associated with conventional chemical methods. In this review, we explore the application of ω-TAms for pharmaceutical production. We discuss the diverse array of reactions available involving ω-TAms and process considerations of their use in both kinetic resolution and asymmetric synthesis. With the aid of specific drug intermediates and APIs, we chart the development of ω-TAms using protein engineering and their contribution to elegant one-pot cascades with other enzymes, including carbonyl reductases (CREDs), hydrolases and monoamine oxidases (MAOs), providing a comprehensive overview of their uses, beginning with initial applications through to the present day.