Dataset Information

Continuous Flow Bioamination of Ketones in Organic Solvents at Controlled Water Activity using Immobilized ?-Transaminases.

ABSTRACT: Compared with biocatalysis in aqueous media, the use of enzymes in neat organic solvents enables increased solubility of hydrophobic substrates and can lead to more favorable thermodynamic equilibria, avoidance of possible hydrolytic side reactions and easier product recovery. ?-Transaminases from Arthrobacter sp. (AsR-?TA) and Chromobacterium violaceum (Cv-?TA) were immobilized on controlled porosity glass metal-ion affinity beads (EziG) and applied in neat organic solvents for the amination of 1-phenoxypropan-2-one with 2-propylamine. The reaction system was investigated in terms of type of carrier material, organic solvents and reaction temperature. Optimal conditions were found with more hydrophobic carrier materials and toluene as reaction solvent. The system's water activity (aw) was controlled via salt hydrate pairs during both the biocatalyst immobilization step and the progress of the reaction in different non-polar solvents. Notably, the two immobilized ?TAs displayed different optimal values of aw, namely 0.7 for EziG3-AsR-?TA and 0.2 for EziG3-Cv-?TA. In general, high catalytic activity was observed in various organic solvents even when a high substrate concentration (450-550?mM) and only one equivalent of 2-propylamine were applied. Under batch conditions, a chemical turnover (TTN) above 13000 was obtained over four subsequent reaction cycles with the same batch of EziG-immobilized ?TA. Finally, the applicability of the immobilized biocatalyst in neat organic solvents was further demonstrated in a continuous flow packed-bed reactor. The flow reactor showed excellent performance without observable loss of enzymatic catalytic activity over several days of operation. In general, ca. 70% conversion was obtained in 72?hours using a 1.82?mL flow reactor and toluene as flow solvent, thus affording a space-time yield of 1.99?g?L-1?h-1. Conversion reached above 90% when the reaction was run up to 120?hours.

SUBMITTER: Bohmer W

PROVIDER: S-EPMC7217232 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Continuous Flow Bioamination of Ketones in Organic Solvents at Controlled Water Activity using Immobilized ω-Transaminases.

Böhmer Wesley W Volkov Alexey A Engelmark Cassimjee Karim K Mutti Francesco G FG

Advanced synthesis & catalysis 20200217 9

Compared with biocatalysis in aqueous media, the use of enzymes in neat organic solvents enables increased solubility of hydrophobic substrates and can lead to more favorable thermodynamic equilibria, avoidance of possible hydrolytic side reactions and easier product recovery. ω-Transaminases from <i>Arthrobacter sp</i>. (AsR-ωTA) and <i>Chromobacterium violaceum</i> (Cv-ωTA) were immobilized on controlled porosity glass metal-ion affinity beads (EziG) and applied in neat organic solvents for th ...[more]

PMID: 32421034

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Project description:Amination of bulky ketones, particularly in (R) configuration, is an attractive chemical conversion; however, known ?-transaminases (?-TAs) show insufficient levels of performance. By applying two screening methods, we discovered 10 amine transaminases from the class III ?-TA family that were 38% to 76% identical to homologues. We present examples of such enzymes preferring bulky ketones over keto acids and aldehydes with stringent (S) selectivity. We also report representatives from the class III ?-TAs capable of converting (R) and (S) amines and bulky ketones and one that can convert amines with longer alkyl substituents. The preference for bulky ketones was associated with the presence of a hairpin region proximal to the conserved Arg414 and residues conforming and close to it. The outward orientation of Arg414 additionally favored the conversion of (R) amines. This configuration was also found to favor the utilization of putrescine as an amine donor, so that class III ?-TAs with Arg414 in outward orientation may participate in vivo in the catabolism of putrescine. The positioning of the conserved Ser231 also contributes to the preference for amines with longer alkyl substituents. Optimal temperatures for activity ranged from 45 to 65°C, and a few enzymes retained ?50% of their activity in water-soluble solvents (up to 50% [vol/vol]). Hence, our results will pave the way to design, in the future, new class III ?-TAs converting bulky ketones and (R) amines for the production of high-value products and to screen for those converting putrescine.IMPORTANCE Amine transaminases of the class III ?-TAs are key enzymes for modification of chemical building blocks, but finding those capable of converting bulky ketones and (R) amines is still challenging. Here, by an extensive analysis of the substrate spectra of 10 class III ?-TAs, we identified a number of residues playing a role in determining the access and positioning of bulky ketones, bulky amines, and (R)- and (S) amines, as well as of environmentally relevant polyamines, particularly putrescine. The results presented can significantly expand future opportunities for designing (R)-specific class III ?-TAs to convert valuable bulky ketones and amines, as well as for deepening the knowledge into the polyamine catabolic pathways.

Dataset Information

Continuous Flow Bioamination of Ketones in Organic Solvents at Controlled Water Activity using Immobilized ?-Transaminases.

Publications

Continuous Flow Bioamination of Ketones in Organic Solvents at Controlled Water Activity using Immobilized ω-Transaminases.

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