The Conformational Transitions and Dynamics of Burkholderia cepacia Lipase Regulated by Water–Oil Interfaces

Abstract

Structural dynamics and conformational transitions are crucial for the activities of enzymes. As one of the most widely used industrial biocatalysts, lipase could be activated by the water–oil interfaces. The interface activations were believed to be dominated by the close-to-open transitions of the lid subdomains. However, the detailed mechanism and the roles of structure transitions are still under debate. In this study, the dynamic structures and conformational transitions of Burkholderia cepacia lipase (LipA) were investigated by combining all-atom molecular dynamics simulations, enhanced sampling simulation, and spectrophotometric assay experiments. The conformational transitions between the lid-open and lid-closed states of LipA in aqueous solution are directly observed by the computational simulation methods. The interactions between the hydrophobic residues on the two lid-subdomains are the driven forces for the LipA closing. Meanwhile, the hydrophobic environment provided by the oil interfaces would separate the interactions between the lid-subdomains and promote the structure opening of LipA. Moreover, our studies demonstrate the opening of the lids structure is insufficient to initiate the interfacial activation, providing explanations for the inability of interfacial activation of many lipases with lid structures.

Lipase A from Bacillus subtilis: Substrate Binding, Conformational Dynamics, and Signatures of a Lid

“…On the other hand, at a lipid–water (or oil–water/air–water) interface, the open state is dominant, and hence lipases can exhibit a higher catalytic rate. The enhanced activity of lipases in the presence of such interfaces is termed “interfacial activation”. − Although the presence of a lid and interfacial activation has been reported in most of the lipases, there are exceptions, such as lipases from coypu, Pseudomonas aeruginosa , and Burkholderia cepacia, which have long amphiphilic lids and do not show interfacial activation, and lipases (from Bacillus subtilis, Streptomyces exfoliatus, and Cavia procellus ), which are characterized as lidless and show no interfacial activation. Further, the Staphylococcus hyicus lipase displays interfacial activation only with some substrates …”