Abstrakt

Protein derived bioactive peptides not only serve as nutrients but can also exert drug-like activity, e.g. antidiabetic, antihypertensive, or antimicrobial, to name a few. Most biopeptides have beneficial effects on health that make them attractive for nutraceutical applications. The majority of bioactive peptides have been obtained from food proteins, but protein-rich by-products generated by agriculture can be used as a cheaper, eco-friendly alternative, since their volume is vast and their utilisation prevents environmental pollution. Among them, one of the most promising and also greatly understudied are chicken feathers, which make up to 10% of the weight of an adult chicken and consist of 90% keratinous proteins. The most potent biopeptides are usually composed of hydrophobic amino acid residues that represent 50-60% of the feather protein sequence. Additionally, peptides containing proline are more resistant to physiological proteolytic degradation, and the feather keratin is proline-rich. The purpose of this study was to apply in silico and in vitro methods to evaluate the potential of chicken feather keratin as a source of biopeptides. The in silico study involved the calculation of the frequency of bioactive fragments occurrence in the keratin sequence, followed by simulation of its hydrolysis using pepsin and subtilisin, and fragmentomic analysis of theoretical products in BIOPEP-UWM. Bioactivity probability and toxicity prediction of the obtained peptides were estimated using PeptideRanker and ToxinPred. The keratin was found to be a potential source of various nontoxic peptides with a total of 15 bioactivities, mostly dipeptidyl peptidase IV and angiotensin-converting enzyme inhibitors. The possible structures of new keratin-derived biopeptides were described. The in vitro study involved extraction of the keratin from chicken feathers using L-cysteine, followed by hydrolysis of the obtained isolate using Alcalase and pepsin under different conditions, and assessment of degree of hydrolysis, and ABTS scavenging activity of the keratin hydrolysates. The highest antioxidative activity was demonstrated by keratin hydrolysate obtained with Alcalase at 55°C, pH 8.5 after 3 hours. The highest degree of hydrolysis was obtained during hydrolysis with Alcalase at 60°C, pH 7.5 for 3 hours. The ABTS scavenging activity of the hydrolysates was not correlated with the degree of hydrolysis. All hydrolysates were soluble in water.

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