Understanding the Plasticity of the α/β Hydrolase Fold: Lid Swapping on the Candida antarctica Lipase B Results in Chimeras with Interesting Biocatalytic Properties

The Candida antarctica lipase B (CALB) has found very extensive use in biocatalysis reactions. Long molecular dynamics simulations of CALB in explicit aqueous solvent confirmed the high mobility of the regions lining the channel that leads into the active site, in particular, of helices alpha 5 and alpha 10. The simulation also confirmed the function of helix alpha 5 as a lid of the lipase. Replacing it with corresponding lid regions from the CALB homologues from Neurospora crassa and Gibberella zeae resulted in two new CALB mutants. Characterization of these revealed several interesting properties, including increased hydrolytic activity on simple esters, specifically substrates with C. branching on the carboxylic side, and much increased enantioselectivity in hydrolysis of racemic ethyl 2-phenylpropanoate (E > 50), which is a common structure of the profen drug family.