Influence of water on enzymatic esterification of racemic ketoprofen in a solventless system

MARÍA VICTORIA TOLEDO; SEBASTIÁN E. COLLINS; LAURA E. BRIAND

Santa Fé

Simposio; IV San Luis School and Conference on Surfaces, Intefaces and Catalysis; 2018

Ketoprofen belongs to the non-steroidal anti-inflammatory NSAIDs group. It is a racemic compound and its pharmacological activity resides only in the S-enantiomer, dexketoprofen. For this reason, administration of pure dexketoprofen would reduce the side effects considering that dose and toxicity will be reduced. One of the most popular methodologies reported to produce dexketoprofen is enzymatic kinetic resolution, and lipases are the most popular enzymes. These enzymes need a certain amount of water to retain the catalytically active three-dimensional structure. Water may have different effects on the rate of lipase-catalyzed reactions. In general, a positive effect is enzymatic activation by water, due to increased internal flexibility, active site polarity and proton conductivity of the enzyme. However, some negative aspects of water are inhibition (interference with substrate binding), formation of a diffusionbarrier for hydrophobic substrates and, when esterification is the main reaction, water interferes as it is a substrate in reversed hydrolysis of the formed ester. Additionally, water can influence lipase enantioselectivity by binding to substrate-binding pockets thereby selectively interfering in the binding of one of the enantiomers of the substrate.Optimal amount of water depends on the solvent and substrates, the type of enzyme and operative conditions.In this context, the optimal amount of water was studied in the esterification of R/S-ketoprofen with ethanol in a solventless system catalyzed by the commercial biocatalyst Novozym® 435 (lipase B from Candida antarctica immobilized on a macroporous resin). Additionally, infrared studies were performed in order to elucidate the effect of water content on the lipase in terms of enzyme flexibility.