Artificial peroxidase of short peptide and hemin co-assemblies with selective chiral catalytic activity in DOPA oxidation

Abstract

Chiral selectivity is one of the merits of natural enzymes in the catalysis of various biochemical reactions, and is also the ambition of artificial enzyme development. In this paper, we have fabricated a kind of artificial peroxidase through the co-assembly of amphiphilic short peptide and hemin. Ac-I3LH-NH2 self-assembled into right handed helical nanofibers, and Ac-I3DH-NH2 self-assembled into left handed helical nanofibers. Ac-I3L/DH-NH2 co-assembled with hemin through the coordination of imidazole group on histidine side chain and Fe(III) in hemin porphyrin ring. Hemin did not destroy the left or right helical morphologies of peptide nanofibers during co-assembly. The activity and chiral selectivity of artificial peroxidases have been assessed with L- and D-type DOPA as the substrates, which can be oxidized into dopachrome by H2O2. The results showed that hemin with right-handed nanofibers of Ac-I3H-NH2 showed higher activity in D-DOPA oxidation, while hemin with left-handed nanofibers of Ac-I3DH-NH2 showed higher activity in L-DOPA oxidation. It was supposed that both the conformation of imidazole group in histidine residues and the handedness of peptide nanofibers affected the chiral selectivity of the artificial peroxidase. The chiral properties have been transferred from the short peptide molecules to self-assembled nanofibers, and finally to the catalytic performance of hemin in the co-assemblies.