The C-terminally shortened analogs of a hexapeptide derived from Lingzhi hydrolysate with enhanced tyrosinase-inhibitory activity

Abstract

Ganoderma lucidum or Lingzhi (Chinese) is a medicinal fungus widely used in traditional medicine as a health supplement. This study was conducted to identify an approach to enhance the anti-tyrosinase activity of a peptide from G. lucidum by chemical modification of its C-terminus. The original peptide was obtained from protease-digested Lingzhi proteins, followed by ultrafiltration (molecular weight cut-off 3 kDa) and C18 solid-phase extraction. The hexapeptide (NH2–VLTCGF–COOH) possessing the anti-tyrosinase activity was identified by liquid chromatography–tandem mass spectrometry (LC-MS/MS). This hexapeptide was subjected to shortening to enhance the anti-tyrosinase activity. Both the original peptide and the shortened peptides were synthesized by solid-phase peptide synthesis. The purity and mass of the synthetic peptide and the modified peptide were evaluated by high-performance liquid chromatography and LC-MS, respectively. Comparison of the tyrosinase activities showed that the modified peptide demonstrated more than 23.27 ± 1.07% activity, which was better than that of the hexapeptide. The structure-related biological activity was explained by molecular docking, wherein the VLT–tyrosinase complex showed two interaction forces: Asn260 and Gly281 through H-bonding and Glu256 through electrostatic interaction. This information could help toward gaining further understanding of the correlation between the anti-tyrosinase activity and the molecular structure of the modified hexapeptide and support its potential use as a safe cosmetic ingredient with tyrosinase-suppressing ability.