Abstract
The enzyme immobilization has been adopted to enhance the activity and stability of enzymes in non-aqueous enzymatic catalysis. However, the activation and stabilization mechanism has been poorly understood on experiments. Thus, we used molecular dynamics simulation to study the adsorption of α-chymotrypsin (α-ChT) on carbon nanotube (CNT) in aqueous solution and heptane media. The results indicate that α-ChT has stronger affinity with CNT in aqueous solution than in heptane media, as confirmed by more adsorption atoms, larger contact area and higher binding free energies. Although the immobilization causes significant structure deviations from the crystal one, no significant changes in secondary structure of the enzyme upon adsorption are observed in the two media. Different from aqueous solution, the stabilization effects on some local regions far from the surface of CNT were observed in heptane media, in particular for S1 pocket, which should contribute to the preservation of specificity reported by experiments. Also, CNT displays to some extent stabilization role in retaining the catalytic H-bond network of the active site in heptane media, which should be associated with the enhanced activity of enzymes. The observations from the work can provide valuable information for improving the catalytic properties of enzymes in non-aqueous media.
Highlights
The enzyme immobilization has been adopted to enhance the activity and stability of enzymes in non-aqueous enzymatic catalysis
The second is a-ChT immobilized to the single walled carbon nanotube (CNT) in aqueous solution, labeled as cnt-wat
In order to be in line with the experimental procedures[17,36] in which the enzymes were first immobilized on carbon nanotubes in aqueous solution and was placed into the organic solvents, we extracted the final snapshot of the complex of the enzyme with CNT from the 100 ns trajectories in aqueous solution as the starting structure to simulate the immobilized enzyme in heptane media
Summary
The enzyme immobilization has been adopted to enhance the activity and stability of enzymes in non-aqueous enzymatic catalysis. Despite of the growing number of computational studies dealing with the solid supports and the proteins in aqueous phase, the studies have been seriously lacked in non-aqueous media so that the understanding of immobilization mechanism in the media has been lagged, which significantly disfavor the effective application of the immobilization method in practice Based on these considerations above, we, performed all-atom MD simulations to study the interaction between a-chymotrypsin (a-ChT) and CNT in nonpolar heptane media and aqueous solution. We further revealed the molecular mechanism concerning the effect of the immobilization of CNT on its structure and stability in the non-polar heptane media, in order to provide valuable information for improving its catalytic properties and advancing its application in nonaqueous media
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