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Inhibitory effect of DMSO on halohydrin dehalogenase: Experimental and computational insights into the influence of an organic co-solvent on the structural and catalytic properties of a biocatalyst

Although the application of organic solvents in biocatalysis is well explored, in-depth understanding of solvent interactions with proteins, in particular oligomeric ones, is still scant. Understanding of these interactions is essential in tailoring enzymes for industrially relevant catalysis in nonaqueous media. In our study, homotetrameric enzyme halohydrin dehalogenase (HHDH) from Agrobacterium radiobacter AD1 (HheC) was investigated, as a model system, in DMSO-water solvent mixtures. DMSO, the most commonly used co-solvent for biocatalytic transformations, was found to act as a mixed-type inhibitor with a prevalent competitive contribution. Already 5% (v/v) DMSO inhibits the activity of HheC by half. Molecular dynamics (MD) simulations showed that DMSO keeps close to Ser-Tyr catalytic residues forming alternate H-bonds with them. Stability measurements paired with differential scanning calorimetry (DSC), dynamic light scattering (DLS) methods and MD studies revealed that HheC conserves structural integrity in content as high as 30% (v/v) DMSO.

halohydrin dehalogenase ; tetrameric enzyme ; DMSO ; co-solvent stability ; MD simulations

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