The amidase activity of Candida antarctica lipase B is dependent on specific structural features of the substrates

The hydrolytic activity of Candida antarctica lipase B (CAL-B) was studied using 15 amides with different linear saturated acyl residues and substituents in the aromatic amine. A strong dependence of the hydrolysis rate on the length of the acyl residue and the substituents groups in the aromatic ring of the amides was demonstrated, with the highest hydrolytic initial reaction rates found for the C10 acyl derivates and benzylamides. The C10 benzylamide, an amide without substituents in the aromatic ring was hydrolyzed almost as fast as capsaicin and five times faster that the corresponding C10 vanillyl derivative. Therefore, a benzylamide bearing the non-linear unsaturated acyl residue of capsaicin (8-methyl-6-nonanenoic acid) was synthesized. This substrate was hydrolyzed four times faster than capsaicin. Although it has been widely claimed that lipases rarely display amidase activity, with this contribution we demonstrate that the amidase activity of CAL-B is dependent on the structural features of the substrate.