Natural enzymes perform impressive catalytic feats with high substrate selectivity due to their particular three-dimensional structures. Inspired by this biological phenomenon, various kinds of molecules, such as self-assembled peptides, polymers, and small molecules, have been designed to mimic natural enzymes. Among these molecules, self-assembled peptides, built from natural amino acids, represent a promising platform for artificial enzymes due to their similarity to natural enzymes. Here we discuss three constitutionally isomeric tetrapeptides, each of which contains two lysine residues functionalized with S-aroylthiooximes (SATOs), a glutamic acid residue, and a histidine residue. These peptides self-assemble in aqueous solution into different morphologies, including a rigid nanohelix, a short but flat nanoribbon, and a mixture of long nanoribbons with nanotoroids. The catalytic activity of these three peptides, determined by monitoring the hydrolysis of p-nitrophenyl acetate, was found to depend on the morphology. The nanocoils promoted catalyzed the reaction about 1.5 times faster than the other peptide nanostructures. We also studied the stereochemical catalytic selectivity of all three catalytic peptides with a pair of enantiomeric substrates, tert-butyloxycarbonyl-l/d-phenylalanine p-nitrophenyl ester. All three peptides accelerated hydrolysis of the l-isomer but barely increased the hydrolysis rate of the d-isomer over a solvent-only control.

Regulating catalytic activity of peptide-based artificial enzymes by supramolecular nanostructures

ACS Fall 2021

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