Abstract
Lunasin, a bioactive peptide initially isolated from soybean, has anticancer, anti-inflammatory, and antioxidant activity. Due its great application value, lunasin seems to be a candidate gene in improving the nutritional value of crops. In this study, lunasin was inserted into the rice genome to evaluate whether it was feasible to express lunasin using the rice expression system and improve the bioactivity of protein in rice for our needs. We generatedlunasin-overexpressing rice lines, and chose three independent transgenic rice lines for further study. The lunasin content in trans-lunasin rice detected by UPLC-MS/MS was 1.01 × 10−3 g·kg−1 dry rice flour with grease removal in the lunasin extracts. The antioxidant efficacy of LET (lunasin-enriched fraction from trans-lunasin rice) and PEW (peptide-enriched fraction from wild type rice) was compared. Due to the presence of lunasin, LET showed higher (p < 0.05) antioxidant activity than PEW. LET exhibited high DPPH radical scavenging activity (IC50 value, 8 g·L−1), strong ABTS+ radical scavenging activity (IC50 value, 1.18 g·L−1), and great oxygen radical scavenging activity (170 μmol·L−1 Trolox equivalents when the concentration reached 4 g·L−1). Moreover, LET presented significantly higher (p < 0.05) anti-inflammatory activity on macrophage cells, and the NO production and the release of pro-inflammatory cytokines (IL-6, MCP1, and TNF-α) were significantly inhibited by LET. However, because of the low purity, LET showed weaker antioxidant and anti-inflammatory activity when compared to the Lunasin standard. These results suggested that it is feasible to use the rice expression system to express the exogenous lunasin in rice, and lunasin-overexpressing rice seems to be a candidate resource for application in functional food. Rice rich in lunasin is beneficial for human health, and could be used as a functional food in the diets of cancer and obese patients in the future.
Highlights
Lunasin, a 43-amino acid peptide with a molecular mass of 5.5 KDa, was initially isolated from soybean [1], and contains an Arg-Gly-Asp cell adhesion motif [2] as well as a conserved chromatin-binding region for binding to histone H3/H4 [3]
PCR and Western blot analysis showed that the lunasin gene was integrated into the rice genome and well expressed in transgenic rice lines L07, L09, and L15 (Figure 1C)
We isolated the total protein from the trans-lunasin and wild type rice, the total protein was separated in a 12% polyacrylamide gel, where the results showed that there was a variety of peptides in the protein extracts (Figure 1D)
Summary
A 43-amino acid peptide with a molecular mass of 5.5 KDa, was initially isolated from soybean [1], and contains an Arg-Gly-Asp cell adhesion motif [2] as well as a conserved chromatin-binding region for binding to histone H3/H4 [3]. Studies have found that the lunasin peptide has anticancer, anti-inflammatory, antioxidant, and cholesterol-lowering activity. The anticancer activity may be due to the inhibition of the acetylation of histone H3 and. Antioxidant activity is due to its abilities to scavenge the reactive oxygen species and inhibit linoleic acid oxidation [7]. Some studies have shown that the lunasin peptide has potential applications to lower the cholesterol and low-density lipoprotein levels through inhibiting the gene expression of some related proteins such as
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