Broad-spectrum antioxidant peptides derived from His residue-containing sequences present in human paraoxonase 1

Hydroxyl or peroxyl radicals and hypochlorous acid (HOCl) are known to cause the oxidation of lipoproteins. Here, we examined Cu(2+)-binding property of paraoxonase 1 (PON1), and antioxidant actions of peptides, resembling His residue-containing sequences in PON1, against oxidations by Cu(2+), peroxyl radicals or HOCl. When Cu(2+)-binding property of PON1 was examined spectrophotometrically, the maximal Cu(2+) binding was achieved at 1:1 molar ratio of PON1: Cu(2+). Additionally, Cu(2+)-catalyzed oxidative inactivation of PON1 was prevented by Ca(2+)-depleted PON1 at 1:1 ratio, but not diethylpyrocarbonate (DEPC)-modified PON1, suggesting the participation of His residue in Cu(2+)-binding. When His-containing peptides were examined for antioxidant actions, those with either His residue at N-terminal position 2 or 3, or His-Pro sequence at C-terminal remarkably prevented Cu(2+)-mediated low density lipoprotein (LDL) oxidation and PON1 inactivation. Especially, FHKALY, FHKY or NHP efficiently prevented Cu(2+)-induced LDL oxidation (24 h), indicating a tight binding of Cu(2+) by peptides. In support of this, the peptide/Cu(2+) complexes exhibited a superoxide-scavenging activity. Separately, in oxidations by 2,2'-azobis-2-amidinopropane hydrochloride or HOCl, the presence of Tyrosine (Tyr) or Cysteine (Cys) residue markedly enhanced antioxidant action of His-containing peptides. These results indicate that His-containing peptides with Tys or Cys residues correspond to broad spectrum antioxidants in oxidation models employing Cu(2+), 2,2'-azobis-2-amidinopropane hydrochloride (AAPH) or HOCl.