博士 / 國立中興大學 / 食品暨應用生物科技學系所 / 97 / Chlorella vulgaris has been the most popular edible microalgae without side effects. Algae essence is an industrial product derived from water extracts of microalgae, and high molecular weight algae protein is a by-product of algae essence production. More than 500 tons of algae essence byproduct produced in Taiwan every year, and re-processed into low economical-value animal feed. However, this algae essence byproduct might become an important protein source for the selection of novel ACE inhibitory peptides, antioxidative peptides and anticancer peptides by enzymatic hydrolysis. In this study, we screened bioactive peptides from algae protein digested with commercial enzymes. A bioactive hendeca-peptide was isolated from the pepsin hydrolysate of algae protein, and Edman degradation revealed its amino acid sequence to be Val-Glu-Cys-Tyr-Gly-Pro-Asn-Arg-Pro-Gln-Phe, the biofuctions were researched as below:
1.Researches on angiotensin I-converting enzyme (ACE) inhibitory activity
The hendeca-peptide with IC50 value of 29.6 uM against ACE suggested a potent amount of ACE inhibitory activity compared with other peptides from the microalgae protein hydrolysates, which have a reported range between 11.4 and 315.3 uM. Inhibitory kinetics revealed a non-competitive binding mode. In addition, the hendeca-peptide completely retained its ACE inhibitory activity in a pH range of 2-10, temperatures of 20-100oC, as well as treated by a gastrointestinal enzyme in vitro, thus indicating its heat-, pH- and gastrointestinal enzyme stability. The combination of the biochemical properties of this isolated hendeca-peptide and a cheap algae protein resource make this process as an attractive alternative for producing high value product for blood pressure regulation as well as water and fluid balance.
2.Researches on antioxidative activity
Algae protein was hydrolyzed using pepsin, and a potent antioxidative peptide of Val-Glu-Cys-Tyr-Gly-Pro-Asn-Arg-Pro-Gln-Phe was separated and isolated. The peptide could efficiently quench a variety of free radicals, including hydroxyl radical, superoxide radical, peroxyl radical, DPPH radical and ABTS radicals, and performed more efficiently than that observed for BHT, Trolox and peptides from marine protein sources in most cases. The peptide also has significant protective effects on DNA and prevents cellular damage caused by hydroxyl radicals. These results suggest that inexpensive algae protein could be a new alternative to produce antioxidative peptides.
3. Researches on AGS inhibitory activity
The peptide fraction isolated from pepsin hydrolysate of algae protein was found to arrest the cell cycle and caused apoptosis in human gastric carcinoma cell lines (AGS); however no cytotoxicity was observed in human lung fibroblasts cell lines (WI-38) in vitro. The peptide fraction has a molecular weight of below 3 KD. The peptide fraction also revealed stronger antioxidative activity toward peroxyl radicals and LDL than natural antioxidant Trolox. A hendeca-peptide with an IC50 value against AGS cells of 256.4 uM was isolated from the peptide fraction and its amino acid sequence was Val-Glu-Cys-Tyr-Gly-Pro-Asn-Arg-Pro-Gln- Phe. The special amino acid sequence and structure of the peptide was important for anticancer effect compared to the synthetic peptide fragments. These results demonstrate that inexpensive algae protein could be a new alternative to produce anticancer peptides.
| Identifer | oai:union.ndltd.org:TW/097NCHU5255001 |
| Creators | I-Chuan Sheih, 謝衣鵑 |
| Contributors | 方 繼 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 118 |
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