Effect of Water Clustering on the Activity of Candida antarctica Lipase B in Organic Medium

Abstract

Abstract:The effect of initial water activity of MTBE (methyl tert-butyl ether) medium on CALB (Candida antarctica lipase B) catalyzed esterification reaction is investigated using experimental methods and classical molecular dynamics (MD) simulations. The experimental kinetic studies show that the initial reaction rate of CALB-catalyzed esterification reaction between butyric acid and ethanol decreases with increasing initial water activity of the medium. The highest rate of esterification is observed at the lowest water activity studied. MD simulations were performed to gain a molecular insight on the effect of initial water activity on the rate of CALB-catalyzed reaction. Our results show that hydration has an insignificant effect on the structure and flexibility of CALB.Rather, it appears that water molecules bind to certain regions ("hot spots") on the CALB surface and form clusters. The size of the water clusters at these hot spot regions gradually increase and expand with increasing water activity. Consequently, the surface area of CALB covered by the water molecules also increases. Specifically, our results indicate that a particular water cluster located close to the active site partially cover the binding pocket of substrate at high water activity. As a consequence, the effective concentration of substrate at the catalytic site decreases. Therefore, the reaction rate slows down with increasing water activity, which correlates well with the observed decrease in the experimentally determined initial reaction rate.

Short‐chain alcohols inactivate an immobilized industrial lipase through two different mechanisms

“…[ 31,40–44 ] The proposed inactivation mechanism gives a prominent role to the thickness of the hydration shell whose increase results in limiting the access of the substrate to the active site. [ 41,43,44 ] In our system, N‐435 samples were freeze‐dried after incubation to completely remove traces of water and alcohols. Based on this procedure, it is reasonable to assume that N‐435 inactivation is mainly due to structural effects.…”

“…CALB activity in organic media was proved sensitive to water content. [ 31,40–44 ] The proposed inactivation mechanism gives a prominent role to the thickness of the hydration shell whose increase results in limiting the access of the substrate to the active site. [ 41,43,44 ] In our system, N‐435 samples were freeze‐dried after incubation to completely remove traces of water and alcohols.…”

Antibodies Processed Using High Dilution Technology Distantly Change Structural Properties of IFNγ Aqueous Solution

“…It is the only method that enables analysis of the vibrations of macromolecules which correspond to large-scale structural movements, as well as the collective dynamics (vibrational and relaxation) of hydrogen-bonded water molecules, making it indispensable in the study of aqueous solutions [17][18][19][20][21][22][23][24][25][26]. It was used to demonstrate the properties of water molecules forming a coat around biological molecules [22,27,28], which may play a role in regulating their activity [29][30][31]. The ability of water exposed to various physical factors to emit THz radiation has been revealed [8,9].…”

Acoustic cavitation assisted lipase B catalysed synthesis of polyethylene glycol stearate in a solvent free system via esterification: synthesis and optimization

“…Hence, all these parameters were optimized to obtain maximum conversion of the acid to PEG stearate. After completion of the reaction the product was separated and purified by the method described in our previous report …”