Understanding water effect on Candida antarctica lipase B activity and enantioselectivity towards secondary alcohols.

• Published in: Journal of Molecular Catalysis B: Enzymatic
• Main Authors: Léonard, Valérie, Marton, Z., Lamare, Sylvain, Hult, Karl, Graber, Marianne
• Other Authors: LIttoral ENvironnement et Sociétés - UMR 7266 (LIENSs), Institut national des sciences de l'Univers (INSU - CNRS)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Department of Biochemistry- KTH, Royal Institute of Technology Stockholm (KTH )
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2009
• Subjects: Lipase Stereoselective catalysis Thermodynamics Thermodynamic activity of water Water adsorption; [SDV.BIO]Life Sciences [q-bio]/Biotechnology; [INFO.INFO-BT]Computer Science [cs]/Biotechnology; Antarc*; Antarctica
• Online Access: https://hal.science/hal-00647583; https://hal.science/hal-00647583/document; https://hal.science/hal-00647583/file/corrected-effet_aw_2_submitted_JMolCatB.pdf; https://doi.org/10.1016/j.molcatb.2009.01.008

6 pages International audience The effect of water activity (aW) on Candida antarctica lipase B (CALB) activity and enantioselectivity towards secondary alcohols was assessed. Experimental results for the resolution of racemic pentan-2-ol, hexan-3-ol, butan-2-ol and octan-4-ol by immobilized CALB-catalyzed acylation with methyl propanoate, were obtained by using a solid/gas reactor. Water and substrate adsorption mechanism on immobilized CALB, were then studied using moisture sorption analyzer and inverse gas chromatography, and the effective hydration state of the biocatalyst when varying aW was defined. The data showed a pronounced aW effect on both activity and enantioselectivity. If secondary alcohol follows the steric rules for being efficiently resolved, water at very low aW increased enantioselectivity by acting predominantly as an enantioselective inhibitor, making the stereospecificity pocket smaller. When increasing aW, water decreased enantioselectivity, due to an unfavourable increase of the entropic term TR-SS‡ of the differential free energy of activation. The "turning point" at which water changed from one predominant role to another would correspond to aW allowing full coverage of polar groups of the immobilized biocatalyst by water molecules.