How do salt bridges affect the activity of enzymes?

Reduction of unfavorable salt bridges on the enzyme surface leads to a higher resistance to organic (co) solvents

Bio VI

Cui, H., Eltoukhy, L., Zhang, L., Markel, U., Jaeger, K. E., Davari, M. D., Schwaneberg, U., Angewandte Chemie, doi.org/10.1002/anie.202101642

The removal of unfavorable salt bridges on the enzyme surface increases the stability of the enzymes in organic solvents as well as the thermal stability

The use of organic (co) solvents (OS) as a reaction medium for biocatalysts is essential for a large number of applications in the chemical industry. OSs are required to solubilize hydrophobic substrates and products. In addition, they enable simple product recovery and shift the reaction equilibrium in the desired direction. However, native enzymes are sensitive to (co) solvents and have a lower activity, which limits their use as biocatalysts in OS. In this publication, we report on an intelligent salt bridge design strategy to simultaneously improve the OS resistance and thermal stability of the model enzyme Bacillus subtilits Lipase A (BSLA) and combined extensive experimental studies of 3450 BSLA variants as well as molecular dynamics simulations of 36 systems. The iterative recombination of four advantageous substitutions resulted in resistant variants with up to 7.6 times (D64K / D144K) improved resistance to three (co) solvents with a simultaneously significantly increased thermal stability (thermal resistance up to 137 times and half-life up to to 3.3 times). Molecular dynamics simulations showed that the local flexibility together with the increased hydration are responsible for the greatly increased resistance in OSs at temperatures of 50-100 ° C. The salt bridge redesign offers a powerful and probably general approach to the design of OS and / or thermally resistant lipases and other α / β hydrolases in the area of ​​protein engineering.

Haiyang Cui is financially supported by the China Scholarship Council (CSC) scholarship. This work was carried out in the Computational Biology department and was supported by computing resources provided by JARA-HPC at RWTH Aachen University (JARA0169 and JARA0187).

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Cui, H., Eltoukhy, L., Zhang, L., Markel, U., Jaeger, K. E., Davari, M. D., Schwaneberg, U., Angewandte Chemie, doi.org/10.1002/anie.202101642

Angewandte Chemie International Edition By removing unfavorable salt bridges on the enzyme surface, the organic solvent and thermal resistance of enzymes can be improved. This strategy leads to locally refined flexibility and increased hydration.