Molecular rules for selectivity in lipase-catalysed acylation of lysine

TL;DR

This study combines experimental and computational methods to uncover molecular rules governing the high selectivity of lipase-catalyzed lysine acylation, emphasizing electrostatic interactions and substrate binding modes.

Contribution

It provides new insights into the molecular basis of selectivity in lipase-catalyzed lysine acylation through integrated experimental and theoretical analysis.

Findings

Lysine is predominantly acylated at the $$-amino group.

Electrostatic interactions influence substrate binding and selectivity.

Proximity of the carboxylate group hinders N$$-acylation.

Abstract

The selectivity of L-lysine acylation by lauric acid catalysed by Candida antarctica lipase B (CALB) was investigated combining experimental and theoretical methodologies. Experiments showed the near-exclusive acylation of lysine $\epsilon$-amino group; only traces of product resulting from the acylation of lysine $\alpha$-amino group were observed fleetingly. Molecular modelling simulations were performed aiming to understand the molecular rules for selectivity. Flexible docking simulations combined with structural investigations into lysine/CALB binding modes also suggested the preferential acylation of lysine $\epsilon$-amino group without, however, excluding the acylation of the lysine $\alpha$-amino group. Electrostatic interaction energy between lysine and the residues covering the catalytic cavity was calculated in order to understand the discrimination between the two lysine amino groups. The results suggests that the proximity of the carboxylate group hinders the binding of the substrate in configurations enabling the N$\alpha$-acylation. Key interactions with the polar region covering the catalytic triad were identified and a plausible explanation for selectivity was proposed.