# Characterization and screening of a novel octapeptide from protein hydrolysates of Crassostrea gigas and its immunomodulatory effects on RAW264.7 cells

## TL;DR

A new oyster-derived peptide was identified that can both stimulate and regulate immune responses, making it useful for functional foods.

## Contribution

A novel immunomodulatory octapeptide (SWDNFLQR) from oyster protein was discovered and shown to regulate immune pathways.

## Key findings

- SWDNFLQR activates TLR and PI3K-Akt pathways to enhance immune cell activity.
- Higher concentrations of SWDNFLQR inhibit NF-κB, reducing excessive inflammation.
- The peptide promotes immune cell proliferation, phagocytosis, and cytokine secretion.

## Abstract

Food-derived bioactive peptides show great potential for functional foods, given their structural adaptability and safety. Crassostrea gigas contains abundant bioactive proteins, but the immunomodulatory mechanism of their peptides remains unclear. In this research, 29 new peptides were identified from papain-hydrolyzed oyster extracts using LC-MS/MS, and target peptide SWDNFLQR with high activity potential was obtained through bioinformatics screening and chemically synthesized. The immunomodulatory properties of SWDNFLQR were assessed through the RAW264.7 cells model and iTRAQ quantitative proteomics. SWDNFLQR enhanced proliferation, phagocytosis, and secretion of NO, TNF-α, and IL-6. It activates Toll-like receptors and the PI3K-Akt signaling pathway, modulating key proteins Fn1 and Prkacb. Notably, higher concentrations of SWDNFLQR specifically inhibited NF-κB pathway activation, indicating its dual immunomodulatory role in stimulating immune responses and mitigating excessive inflammation. This positions SWDNFLQR as a valuable component for the formulation of anti-inflammatory and immune-regulating functional foods.

•A new type of oyster peptide (SWDNFLQR) with immunomodulatory activity was identified and screened out.•Bidirectional immune regulation‌ achieved by activating TLR/PI3K-Akt while inhibiting NF-κB pathways.•Integrative approach combining LC-MS/MS, bioinformatics screening, synthetic chemistry, and proteomics.

A new type of oyster peptide (SWDNFLQR) with immunomodulatory activity was identified and screened out.

Bidirectional immune regulation‌ achieved by activating TLR/PI3K-Akt while inhibiting NF-κB pathways.

Integrative approach combining LC-MS/MS, bioinformatics screening, synthetic chemistry, and proteomics.