Nutritional and Structural Characteristics of Selenium-Enriched Protein from Pleurotus eryngii and Its Alleviative Effect on Lead Toxicity

The diet is the main way by which lead enters and accumulates in the human body, causing damage to various systems such as the immune and metabolic systems. It has been demonstrated that selenium supplementation can significantly alleviate the harm of lead exposure to the body. In this study, speciation of selenium in selenium-enriched protein from Pleurotus eryngii (SePEP) was investigated by high performance liquid chromatography-inductively coupled plasma mass spectrometry and the protein secondary structure of SePEP was analyzed by Fourier transform infrared spectroscopy. The alleviative effect of in vitro digested SePEP was evaluated on Pb²⁺-induced cytotoxicity in RAW264.7 cells. The results showed that the selenium content of SePEP was (360.64 ± 3.11) mg/kg, and the main species of selenium included selenomethionine (SeMet, (48.04 ± 0.64)%), selenocystine (SeCys₂, (31.91 ± 0.51)%), and methylselenocysteine (MeSeCys, (14.65 ± 0.36)%). The addition of selenium significantly promoted the formation of amino acids and changed protein structures, resulting in an increase in α-helix structure from (20.30 ± 0.87)% to (25.00 ± 1.60)%, and a decrease in random coil content from (20.38 ± 0.84)% to (13.85 ± 1.66)%. Moreover, the contents of total sulfhydryl and disulfide bonds and surface hydrophobicity were significantly increased (P < 0.05). After adding digested SePEP, the viability of RAW264.7 cells treated with Pb²⁺ was significantly increased from approximately 50% to (76.95 ± 6.95)%, the release amount of lactate dehydrogenase in the culture medium was decreased by 57.45%, and the release of three pro-inflammatory cytokines: interleukin (IL)-6, IL-8 and tumor necrosis factor α was significantly inhibited (P < 0.05), indicating that SePEP digestion products could alleviate Pb²⁺ exposure-induced damage in RAW264.7 cells. These results of this study can provide a basis for the development of safe and effective selenium-enriched protein-based foods for alleviating lead toxicity.