Biocatalytic Promiscuity

Unexpected three-component domino synthesis of pyridin-2-ones catalyzed by promiscuous acylase in non-aqueous solvent

The Acylase "Amano" (AA)-catalyzed synthesis of valuable pyridin-2-ones via domino Knoevenagel condensation-Michael addition-intramolecular cyclization-oxidization reaction between aldehyde, cyanoacetamide and ethyl acetoacetate or cyclohexyl acetoacetate was developed in the sense of a one-pot strategy. Various aliphatic, aromatic and hetero-aromatic pyridin-2-ones could also be produced in the reaction. The mechanism was illustrated according to the controlled reaction, pyridin-2-one was formed via the oxidization by oxygen at the final step. This simple and efficient enzymatic domino reaction not only widens its application of AA to organic synthesis, but is also an attractive way for the synthesis of heterocyclic compounds.

The promiscuous binding of pharmaceutical drugs and their transporter-mediated uptake into cells: what we (need to) know and how we can do so

A recent paper in this journal sought to counter evidence for the role of transport proteins in effecting drug uptake into cells, and questions that transporters can recognize drug molecules in addition to their endogenous substrates. However, there is abundant evidence that both drugs and proteins are highly promiscuous. Most proteins bind to many drugs and most drugs bind to multiple proteins (on average more than six), including transporters (mutations in these can determine resistance); most drugs are known to recognise at least one transporter. In this response, we alert readers to the relevant evidence that exists or is required. This needs to be acquired in cells that contain the relevant proteins, and we highlight an experimental system for simultaneous genome-wide assessment of carrier-mediated uptake in a eukaryotic cell (yeast).

Protease-catalysed direct asymmetric Mannich reaction in organic solvent

We reported the first enzyme-catalysed, direct, three-component asymmetric Mannich reaction using protease type XIV from Streptomyces griseus (SGP) in acetonitrile. Yields of up to 92% with enantioselectivities of up to 88% e.e. and diastereoselectivities of up to 92:8 (syn:anti) were achieved under the optimised conditions. This enzyme's catalytic promiscuity expands the application of this biocatalyst and provides a potential alternative method for asymmetric Mannich reactions.

Recent advances in rational approaches for enzyme engineering

Enzymes are an attractive alternative in the asymmetric syntheses of chiral building blocks. To meet the requirements of industrial biotechnology and to introduce new functionalities, the enzymes need to be optimized by protein engineering. This article specifically reviews rational approaches for enzyme engineering and de novo enzyme design involving structure-based approaches developed in recent years for improvement of the enzymes’ performance, broadened substrate range, and creation of novel functionalities to obtain products with high added value for industrial applications.

Unusual C=C bond isomerization of an α,β-unsaturated γ-butyrolactone catalysed by flavoproteins from the old yellow enzyme family

An unexpected, redox-neutral C=C bond isomerization of a γ-butyrolactone bearing an exo-methylene unit to the thermodynamically more favoured endo isomer (k_cat = 0.076 s⁻¹) catalysed by flavoproteins from the Old Yellow Enzyme family was discovered. Theoretical calculations and kinetic data support a mechanism through which the isomerization proceeds through FMN-mediated hydride addition onto exo-Cβ, followed by hydride abstraction from endo-Cβ′, which is in line with the well-established C=C bond bioreduction of OYEs. This new isomerase activity enriches the catalytic versatility of ene-reductases.

Computational design of a Diels-Alderase from a thermophilic esterase: the importance of dynamics

A novel computational Diels-Alderase design, based on a relatively rare form of carboxylesterase from Geobacillus stearothermophilus, is presented and theoretically evaluated. The structure was found by mining the PDB for a suitable oxyanion hole-containing structure, followed by a combinatorial approach to find suitable substrates and rational mutations. Four lead designs were selected and thoroughly modeled to obtain realistic estimates of substrate binding and prearrangement. Molecular dynamics simulations and DFT calculations were used to optimize and estimate binding affinity and activation energies. A large quantum chemical model was used to capture the salient interactions in the crucial transition state (TS). Our quantitative estimation of kinetic parameters was validated against four experimentally characterized Diels-Alderases with good results. The final designs in this work are predicted to have rate enhancements of ≈ 10(3)-10(6) and high predicted proficiencies. This work emphasizes the importance of considering protein dynamics in the design approach, and provides a quantitative estimate of the how the TS stabilization observed in most de novo and redesigned enzymes is decreased compared to a minimal, 'ideal' model. The presented design is highly interesting for further optimization and applications since it is based on a thermophilic enzyme (T (opt) = 70 °C).