Promiscuous Reactions Catalyzed by Glutamate Dehydrogenase Induced with Amino Acid Deep Eutectic Solvents and Electric Field Analysis

The catalytic promiscuity of glutamate dehydrogenase (GDH) with a heme-binding domain was studied. Eight amino acid deep eutectic solvents (AA-DESs) acted as both substrates and solvents in the activity and structural stability of the enzyme. The activities of 3AOG-6NZX with 10% (v/v) AA-DESs, namely, l-Asp-DES, l-Lys-DES, l-Cys-DES, and l-Phe-DES were 1206.3%, 110.3%, 928.3%, and 146.7% of the activity observed with amino acids as substrates, respectively. The electric field of the active site binding with Glu and Asp was compared, which reveals that distinct electric field topologies influence enzyme activity. Upon further addition of 15 μM heme, the activity of 3AOG-6NZX in 10% (v/v) l-Asp-DES showed a 197.7% enhancement, indicating that the binding of heme changed the electric potential and improved the activity. Furthermore, molecular dynamic simulations (MDS) revealed the regulation of electric fields by DES through its manipulation to enable a substrate switch. Understanding enzyme behaviors in DESs enabled the design of promising enzyme-compatible and tunable solvents.