Structural investigations of Candida antarctica Lipase B in ethanol for catalysis in the food industry

Candida antarctica lipase B (CALB) is one of the most widely studied enzymes, due to its high selectivity and catalytic activity in organic and polymer synthesis. Given the great interest in knowing the behaviour of CALB in presence of specific organic solvents, the molecular mechanism of the deactivation of the enzyme by primary alcohols was already investigated by several researchers. In this contest, in order to understand the defective activity of the lipase, we addressed the inhibition pathways of CALB by ethanol. The structural modifications of CALB in an ethanol-water mixture were evaluated in the present work considering that the catalytic activity decreases in such a mixture. The present work reports two crystal structures of the lipase in presence of ethanol refined with specific crystallographic software tools, namely WinCoot and Phenix. WinCoot is the program used for any kind of correction at the atomic level to the crystal structure because capable to provide specific tools for intervening in the enzyme structure. Then, the obtained model was refined and validated the modifications with Phenix. Having a molecular description of the interaction between solvent and enzyme is a prerequisite to a qualitative understanding of enzymatic activity in organic solvents. Keywords: Candida antarctica, lipase B, esterification, ethanol inhibition