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The widespread UbiD enzyme family utilises the prFMN cofactor to achieve reversible decarboxylation of acrylic and (hetero)aromatic compounds. The reaction with acrylic compounds based on reversible 1,3-dipolar cycloaddition between substrate and prFMN occurs within the confines of the active site. In contrast, during aromatic acid decarboxylation, substantial rearrangement of the substrate aromatic moiety associated with covalent catalysis presents a molecular dynamic challenge. Here we determine the crystal structures of the multi-subunit vanillic acid decarboxylase VdcCD. We demonstrate that the small VdcD subunit acts as an allosteric activator of the UbiD-like VdcC. Comparison of distinct VdcCD structures reveals domain motion of the prFMN-binding domain directly affects active site architecture. Docking of substrate and prFMN-adduct species reveals active site reorganisation coupled to domain motion supports rearrangement of the substrate aromatic moiety. Together with kinetic solvent viscosity effects, this establishes prFMN covalent catalysis of aromatic (de)carboxylation is afforded by UbiD dynamics., Understanding the structure and dynamics of enzymes is important for a number of applications. Here, the authors report on the crystal structure of vanillic acid decarboxylase, and show how the dynamics of the UbiD superfamily enzymes relate to the covalent catalysis of aromatic (de)carboxylation.

In recent years, (de)carboxylases that catalyze reversible (de)carboxylation have been targeted for application as carboxylation catalysts. This has led to the development of proof-of-concept (bio)synthetic CO2 fixation routes for chemical production. However, further progress towards industrial application has been hampered by the thermodynamic constraint that accompanies fixing CO2 to organic molecules. In this Review, biocatalytic carboxylation methods are discussed with emphases on the diverse strategies devised to alleviate the inherent thermodynamic constraints and their application in synthetic CO2 -fixation cascades.

Allylic amines are a versatile class of synthetic precursors of many valuable nitrogen-containing organic compounds, including pharmaceuticals. Enzymatic allylic amination methods provide a sustainable route to these compounds but are often restricted to allylic primary amines. We report a biocatalytic system for the reductive N-allylation of primary and secondary amines, using biomass-derivable cinnamic acids. The two-step one-pot system comprises an initial carboxylate reduction step catalyzed by a carboxylic acid reductase to generate the corresponding α,β-unsaturated aldehyde in situ. This is followed by reductive amination of the aldehyde catalyzed by a bacterial reductive aminase pIR23 or BacRedAm to yield the corresponding allylic amine. We exploited pIR23, a prototype bacterial reductive aminase, self-sufficient in catalyzing formal reductive amination of α,β-unsaturated aldehydes with various amines, generating a broad range of secondary and tertiary amines accessed in up to 94% conversion under mild reaction conditions. Analysis of products isolated from preparative reactions demonstrated that only selective hydrogenation of the C=N bond had occurred, preserving the adjacent alkene moiety. This process represents an environmentally benign and sustainable approach for the synthesis of secondary and tertiary allylic amine frameworks, using renewable allylating reagents and avoiding harsh reaction conditions. The selectivity of the system ensures that bis-allylation of the alkylamines and (over)reduction of the alkene moiety are avoided.

In recent years, (de)carboxylases that catalyze reversible (de)carboxylation have been targeted for application as carboxylation catalysts. This has led to the development of proof‐of‐concept (bio)synthetic CO2 fixation routes for chemical production. However, further progress towards industrial application has been hampered by the thermodynamic constraint that accompanies fixing CO2 to organic molecules. In this Review, biocatalytic carboxylation methods are discussed with emphases on the diverse strategies devised to alleviate the inherent thermodynamic constraints and their application in synthetic CO2‐fixation cascades., The fix is in: This Review examines progress made in developing (de)carboxylases for application in organic synthesis for CO2 fixing reactions. It highlights the synthetic scope of promising (de)carboxylase enzymes and the numerous strategies devised to increase enzymatic carboxylation yield, including application of (de)carboxylases in synthetic cascades.

The direct C-H carboxylation of aromatic compounds is an attractive route to the corresponding carboxylic acids, but remains challenging under mild conditions. It has been proposed that the first step in anaerobic microbial degradation of recalcitrant aromatic compounds is a UbiD-mediated carboxylation. In this study, we use the UbiD enzyme ferulic acid decarboxylase (Fdc) in combination with a carboxylic acid reductase to create aromatic degradation-inspired cascade reactions, leading to efficient functionalization of styrene through CO

The direct C–H carboxylation of aromatic compounds is an attractive route to the corresponding carboxylic acids, but remains challenging under mild conditions. It has been proposed that the first step in anaerobic microbial degradation of recalcitrant aromatic compounds is a UbiD-mediated carboxylation. In this study, we use the UbiD enzyme ferulic acid decarboxylase (Fdc) in combination with a carboxylic acid reductase to create aromatic degradation-inspired cascade reactions, leading to efficient functionalization of styrene through CO2 fixation. We reveal that rational structure-guided laboratory evolution can expand the substrate scope of Fdc, resulting in activity on a range of mono- and bicyclic aromatic compounds through a single mutation. Selected variants demonstrated 150-fold improvement in the conversion of coumarillic acid to benzofuran + CO2 and unlocked reactivity towards naphthoic acid. Our data demonstrate that UbiD-mediated C–H activation is a versatile tool for the transformation of aryl/alkene compounds and CO2 into commodity chemicals. Biocatalytic cascade reactions using engineered variants of ferulic acid decarboxylase coupled to carboxylic acid reductase utilize carbon dioxide fixation to enable the carboxylation and functionalization of styrene and other aromatic compounds.