Abstract
Background: Lactoferrin (LF) exhibits multiple beneficial biological activities and thus has been used as a health food and additive. To broaden its application in the food industry, the porcine LF (pLF) gene has been engineered into rice to produce recombinant LF (rpLF) for use as a food additive. The iron-binding and antimicrobial activities of rpLF and its positive effects on early weaned piglets have been previously evaluated, yet several features, such as the signal peptide removal, glycosylation sites and antioxidant activity of rpLF, have not been fully characterized. Objective: In this work, the rice-produced rpLF was purified and its biochemical structure and antioxidant activities characterized. Methods: HPLC, Western blot, PAS/VVL/PNA staining, Edman degradation assay, MALDI-TOF, LC-MS/MS and antioxidant activity assays were performed. Results: The results showed that this purified rpLF is a mature form of LF; its signal peptide was correctly removed, and two N-glycosylation sites located at N365 and N472 were identified. The molecular mass heterogeneity of rpLF could be eliminated by treatment with PNGase glycosidase, suggesting that different degrees of N-glycosylation occur in rpLF. A series of assays including the iron chelating activity, reducing power assay, lipid peroxidase activity and radical-scavenging activity showed that the antioxidant activity of rice-produced rpLF was equivalent to that of bovine LF. Conclusion: Rice-produced rpLF was correctly processed post-translationally and displayed antioxidant activity equivalent to that of bovine LF; thus, rice-produced rpLF can be recognized as a plant-based antioxidant to be used as a functional additive in animal feed and for the food industry.
Highlights
The results showed that this purified recombinant porcine LF (rpLF) is a mature form of LF; its signal peptide was correctly removed, and two N-glycosylation sites located at N365 and N472 were identified
The molecular mass heterogeneity of rpLF could be eliminated by treatment with PNGase glycosidase, suggesting that different degrees of N-glycosylation occur in rpLF
Rice-produced rpLF was correctly processed post-translationally and displayed antioxidant activity equivalent to that of bovine LF; riceproduced rpLF can be recognized as a plant-based antioxidant to be used as a functional additive in animal feed and for the food industry
Summary
The primary structure of LF contains various Cys residues that allow the formation of intramolecular disulfide bridges and Asn residues in the N- and C-terminal lobes that provide potential N-glycosylation sites to which complex and high-mannose-type glycans are linked [10, 11]. These glycans are structurally heterogeneous, resulting in various molecular mass isoforms of LFs, and this heterogeneity may be responsible for various biological functions [10 - 12]. The ironbinding and antimicrobial activities of rpLF and its positive effects on early weaned piglets have been previously evaluated, yet several features, such as the signal peptide removal, glycosylation sites and antioxidant activity of rpLF, have not been fully characterized
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