LC-MS/MS Identification of a Myeloperoxidase-Targeting Antioxidant Peptide from Black Soybean

The rising prevalence of oxidative stress-related diseases has increased the demand for natural antioxidants. In response, a research group identified and characterized a novel antioxidant peptide from black soybean (Glycine max) aqueous extracts that targets myeloperoxidase (MPO), a key enzyme involved in oxidative damage. Peptide components were profiled by liquid chromatography-tandem mass spectrometry (LC-MS/MS). A paper based on their study was published in Frontiers in Nutrition (1).

Highly reactive molecules generated as byproducts of cellular metabolism, including hydrogen peroxide (H₂O₂), hydroxyl radicals (OH), and others, reactive oxygen species (ROS) play essential roles in various biological processes such as cell signaling, immune defense, and regulation of cell proliferation. When the production of ROS exceeds the capacity of the endogenous antioxidant defense system, however, the result is oxidative stress (2,3). An excess of ROS may induce oxidative modifications of biomacromolecules, including lipid peroxidation, protein carbonylation, and DNA damage, which can disrupt cellular structure and function (4). Increasing evidence has demonstrated that oxidative stress is closely associated with the onset and progression of numerous chronic diseases as well as the development of neurodegenerative disorders such as Alzheimer’s disease, while also playing a critical role in the pathogenesis of atherosclerosis through the stimulation of endothelial dysfunction and inflammatory responses (5,6).

Myeloperoxidase (MPO), an endogenous peroxidase enzyme, is predominantly expressed and secreted by activated neutrophils and plays a critical role in the host immune defense system (7). Excessive activation of MPO, however, may result in the overproduction of ROS, which would overcome the body’s antioxidant defense mechanisms and contribute to the progression of the chronic diseases mentioned earlier. Two major intervention strategies have been proposed to counteract MPO-mediated oxidative damage: inhibition of MPO activity and scavenging of free radicals. MPO inhibitors can directly block its catalytic activity, reducing the generation of harmful oxidative products; their antioxidant potential can also contribute to redox homeostasis by directly scavenging already-existing ROS (8).

Black soybean is a traditional legume crop characterized by its black seed coat, black soybean has been cultivated in China for thousands of years, with the country remaining the largest producer and consumer of the crop globally (9). According to the authors of the study, “Black soybean was selected as the research subject due to its promising potential as a source of novel antioxidant peptides. A candidate peptide with the strongest predicted binding affinity to MPO was first screened through molecular docking, and its interaction was further evaluated using molecular dynamics simulation. The direct binding interaction between the synthetic peptide and MPO protein was then validated using SPR analysis.” (1)

The researchers selected the peptide VPNHFNAP via molecular docking and dynamics simulations against MPO, followed by binding affinity validation using surface plasmon resonance (SPR). Antioxidant capacity was assessed through 2,2-diphenyl-1-picrylhydrazyl (DPPH) (10)/ 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (10) radical scavenging assays. Cytoprotective effects were evaluated in HaCaT cells under H₂O₂-induced oxidative stress (1).

The researchers found that VPNHFNAP exhibited strong MPO binding and radical scavenging activity. Molecular docking revealed hydrogen bonds with MPO's His95 and Arg239. In cellular models, 50 μM VPNHFNAP increased viability over twofold, and reduced ROS levels as well (1).

This study, the researchers reported, “establishes VPNHFNAP as a potent MPO-targeted antioxidant peptide through an integrated computational-experimental strategy. Its dual function (direct radical scavenging and cellular protection) highlights potential applications in functional foods or cosmeceuticals. The screening framework also advances plant peptide discovery by combining bioinformatics with multi-level validation.” (1)

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References

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