Biological Activities of Bioactive Peptides

Bioactive peptides, usually containing 3 to 20 amino acid residues, are derived from food proteins and can have a positive impact on human health. Once absorbed by the human body, the bioactive peptide brings various benefits, such as preventing diseases or regulating the physiological system. Bioactive peptides have a variety of different biological activities, including antibacterial activity, immune activity, antioxidant activity, anti-hypertensive activity, cholesterol-lowering activity, mineral absorption promotion activity, growth-promoting activity, and anti-tumor activity.

1 Antibacterial activity

Antibacterial peptides are commonly obtained from animals, plants, microorganisms, or immune insects. Most of them are alkaline or positive ion peptides with less than 50 amino acids, rich in lysine and arginine. Antimicrobial peptides are hydrophilic and lipophilic, which can form small pores under the cell membrane of sensitive bacteria, causing cell growth to be inhibited until death. Antimicrobial peptides have powerful killing effects on some bacteria, fungi, protozoa, viruses, and cancer cells. Clinical trials have also shown that antimicrobial peptides can enhance the body's ability to resist pathogenic microorganisms. It's not easy for Antimicrobial peptides to produce drug resistance in the body, so they have a wide range of application prospects.

2 Immune activity

Many biologically active peptides derived from animals and plants have immunomodulatory effects. These immunologically active peptides can interact with the intestinal mucosa and lymphoid tissues, and can also pass through the intestinal wall freely and directly interact with peripheral lymphocytes. As an immune factor, thymosin has been used in clinical medicine and the treatment of anti-infection and immunodeficiency. Researchers found that both soybean protein and casein hydrolysate can stimulate the transformation of peripheral blood lymphocytes in 10-day-old piglets induced by PHA to varying degrees, and the soy protein hydrolysate has the strongest effect on promoting lymphocyte transformation. Immune active peptides mainly regulate the immune function of the body by regulating the function of lymphocytes, affecting the function of monocytes and macrophages, regulating the secretion of cytokines, and influencing calcium ion conduction of lymphocytes. Besides, immune active peptides can stimulate the proliferation of lymphocytes in the body, enhance the phagocytic function of macrophages, improve the body's ability to resist infection by external pathogens, and reduce the body's morbidity.

3 Antioxidant activity

Antioxidant active peptides added to meat products can prevent the failure of oxidized fatty acids, and they have broad application prospects in food and animal feed as preservatives. Studies have found that there are also peptides with antioxidant activity in soybean proteolysis. In addition, the carnosine present in animal muscles can inhibit lipid oxidation catalyzed by iron, hemoglobin, lipid oxidase, and singlet oxygen in vitro. As natural antioxidants, antioxidant active peptides such as carnosine, glutathione, and soybean proteolysis have the characteristics of low toxicity and high efficiency. Certain peptides and protein hydrolysates can play the role of heavy metal scavengers and hydrogen peroxide decomposition promoters, which can reduce the rate of auto-oxidation and the hydrogen peroxide content of fats, thereby reducing the generation of free radicals. For instance, antioxidant peptide A is a short peptide, which contains alternative aromatic or sulfur-containing amino acids. The side chains of it are believed to contribute to strong radical scavenging activities of peptides in cancer cells.

4 Antihypertensive activity

Antihypertensive peptides mainly affect blood pressure by inhibiting angiotensin-I converting enzymes, and then affecting the renin-angiotensin-aldosterone system. It is generally believed that the C-terminal Pro, Phe, and Tyr of antihypertensive peptides or the hydrophobic amino acids contained in the sequence are necessary to maintain high activity. There are roughly 4 sources of known antihypertensive peptides: peptides from milk proteins; peptides from yogurt; peptides from fish and shellfish (sardines, tuna); peptides from plants (figs).

5 Cholesterol-lowering activity

Studies found that soybean peptides can lower serum cholesterol and have special advantages compared with soybean protein. The cholesterol-lowering effect of soybean peptides mainly stimulates the secretion of thyroid hormones, promotes bile acidification of cholesterol, and increases the excretion of cholesterol in the feces, thereby reducing the cholesterol content in the blood.

6 Mineral absorption promotion activity

Most of these peptides have phosphoserine clusters and glutamate clusters as active centers, such as casein phosphopeptides. The mechanism of action of such peptides is that a large number of seryl phosphate clusters contained in its active center accumulate plentiful negative charges, which can form chelates with metal ions. This chelate does not precipitate under alkaline conditions, thereby promoting the absorption of metal ions. Soy peptides have active groups that can be effectively combined with calcium and other trace elements, thereby forming organic calcium polypeptide complexes with these substances, which greatly promote calcium absorption. In addition, bioactive peptides can also be combined with iron, selenium, zinc, and other trace elements to form organometallic complex peptides.

7 Growth-promoting activity

Growth-promoting peptides can accelerate cell growth and differentiation. For example, the enzymatic hydrolysate of soy protein can stimulate the growth of bacteria, especially lactic acid bacteria. Peptides extracted from eggs can promote cell growth and DNA synthesis.

8 Anti-tumor activity

A variety of biologically active peptides were found to have anti-tumor activity and are thereby called tumor suppressor peptides, some of which are not only limited to nutrients with tumor-suppressive effects, but also have been developed into anti-tumor drugs, becoming a research hotspot in the search for anti-cancer drugs. Natural tumor suppressor peptides are mainly extracted from marine organisms, amphibians, and various plants, and some have been put into clinical use as anti-cancer drugs. These tumor suppressor peptides mainly exert anti-tumor effects by directly inhibiting tumor growth and tumor angiogenesis and activating the body's immune system.

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