Poster Presentation The 16th Australian Peptide Conference 2025

Elucidating the role of L-tyrosine in enhancing the antioxidant properties of β-Casein-derived peptides (#220)

Yasuri Amarasekara 1 2 , Narsimha Reddy 3 , Helena Nevalainen 4 , Junior Te'o 4 , Anwar Sunna 1 2
  1. ARC Industrial Transformation Training Centre for Facilitate Advancement of Australia's Bioactives (FAAB), North Ryde, NSW 2109, Australia
  2. Macquarie University, School of Natural Sciences, North Ryde, NSW 2019, Australia
  3. Western Sydney University, School of Science, Parramatta, NSW 2150, Australia
  4. Change Foods , Palo Alto, CA 94306, USA

Bioactive peptides with antioxidant potential are emerging as important agents in the development of peptide-based therapeutics and functional foods1. Among amino acid residues that contribute to radical-scavenging activity, L-tyrosine stands out because of its phenolic hydroxyl group, which aids in neutralising reactive oxygen species (ROS)2,3. However, the specific mechanisms by which tyrosine enhances antioxidant function within peptide sequences remain underexplored.

This study compares two structurally similar β-casein-derived peptides, EMPFPKY(βCN) and EMPFPK(βCN), which differ by a single C-terminal tyrosine residue, to investigate its role in antioxidant activity. ABTS, FRAP, and DPPH assays revealed significantly enhanced radical scavenging activity for EMPFPKY(βCN) across all platforms (p < 0.0001), highlighting the contribution of tyrosine to chemical antioxidant function 4.

To assess physiological relevance, Caco-2 cell-based oxidative stress assays showed that EMPFPKY(βCN) conferred greater cytoprotective effects, confirming its functional advantage in a biological context. Molecular docking further revealed stronger binding affinity of EMPFPKY(βCN) to Keap1 (−7.8 kcal/mol), suggesting potential modulation of the Keap1–Nrf2 antioxidant pathway 5.

Quantum chemical analysis supported these findings: the Highest Occupied Molecular Orbital (HOMO) in EMPFPKY(βCN) was localised on the tyrosine phenol ring, enabling efficient electron donation. In contrast, EMPFPK(βCN) displayed a more delocalised HOMO, correlating with lower redox activity and reduced antioxidant potential6.

This integrative approach, combining chemical assays, cell-based analysis, molecular docking, and quantum chemistry, demonstrates the critical role of tyrosine in modulating antioxidant activity in β-casein-derived peptides. These findings provide a structure–activity framework to support the rational design of peptide-based antioxidants for pharmaceutical, nutraceutical, and functional food applications. 

Keywords:

L-tyrosine; Antioxidant peptides; Caseins; Free radicals; Keap1-Nrf2; HOMO-LUMO; Caco-2; Structure–function

 

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