What are the uses of peptides ?

2021-01-29

Peptides are biologically active substances involved in various cell functions in organisms. It has been more than 40 years since biochemists synthesized peptides by artificial methods. With the rapid development of molecular biology and biochemical technology, the research of peptides has made amazing and epoch-making progress. It has been discovered that there are tens of thousands of polypeptides in organisms, and it has been discovered that all cells can synthesize polypeptides. At the same time, almost all cells are also regulated by peptides, which are involved in various fields such as hormones, nerves, cell growth and reproduction. For quite some time in the future, there will be a glorious period in human research and application of peptides, so this century is a world of peptides. At present, the applications of peptides are mainly concentrated in peptide drugs, peptide drug carriers, tissue engineering materials, and peptide nutritional foods.


1. Anti-tumor peptides


The occurrence of tumors is the result of multiple causes, but ultimately all involve the regulation of oncogene expression. Different tumors require different enzymes and other regulatory factors. Selecting specific small peptides to act on the regulatory factors needed for tumorigenesis and blocking the active site can prevent tumorigenesis. Many tumor-related genes and tumor production regulatory factors have now been discovered, and the screening of peptides that specifically bind to these targets has become a new hot spot in the search for anti-cancer drugs. American scholars have discovered a small peptide (6 amino acids), which can significantly inhibit the growth of adenocarcinoma in the body, including lung, stomach, and large intestine adenocarcinoma, opening up a new way to treat this malignant tumor with high mortality. Swiss scientists discovered another small peptide (8 amino acids) that can enter tumor cells, activate the anti-oncogene P53, and induce tumor cell apoptosis.


2. Antiviral peptides


Virus infection generally undergoes multiple stages such as adsorption (host cell), penetration, uncoating, nucleic acid replication, transcription and translation, and packaging. Blocking any process can prevent virus replication. The most effective antiviral drugs should act in the two stages of virus adsorption and nucleic acid replication. Therefore, the screening of antiviral drugs mainly focuses on these two stages of virus replication. Viruses bind to specific receptors on host cells to adsorb cells, and rely on their own specific proteases for protein processing and nucleic acid replication. Therefore, peptides that bind to host cell receptors or peptides that bind to active sites such as viral proteases can be screened from the peptide library for antiviral therapy, which will become the largest market for alternative antibiotics.


3. Peptide-oriented drugs


Many toxins (such as Pseudomonas aeruginosa exotoxin) and cytokines (such as interleukin series) are known to have strong tumor cytotoxicity, but they can also damage normal cells in long-term or large amounts of human use. Fusion of polypeptides that can specifically bind to tumor cells with these active factors can specifically concentrate these active factors on the tumor site, which can greatly reduce the concentration of toxins and cytokines and reduce their side effects. For example, there are receptors for epidermal growth factor on the surface of many tumor cells, and the number of receptors is dozens or even hundreds of times higher than that on normal cells. Fusion of toxins or anti-tumor cytokines with epidermal growth factor can combine these active factors. It specifically aggregates to tumor cells, and several domestic and foreign companies have successfully expressed epidermal growth factor and Pseudomonas exotoxin fusion. Small peptides that can specifically bind to tumor antigens are screened from the peptide library, and can also be used for targeting drugs. Because of their small molecular weight, they are more suitable for targeting drugs than murine monoclonal antibodies.


4. Cytokine mimic peptide


The use of known cytokine receptors to screen cytokine mimic peptides from peptide libraries has become a research hotspot at home and abroad in recent years. The mimic peptides of human erythropoietin, human thrombopoietin, human growth hormone, human nerve growth factor and interleukin 1 have been screened abroad. The amino acid sequences of these mimetic peptides are different from the amino acid sequences of their corresponding cytokines, but they have cytokine activity and have the advantage of small molecular weight. These cytokine mimetic peptides are in the preclinical or clinical research stage.

5. Antibacterial active peptide


When insects are stimulated by the external environment, they produce a large number of cationic peptides with antibacterial activity. More than 100 kinds of antibacterial peptides have been screened. In vivo and in vitro experiments have confirmed that multiple antibacterial peptides not only have strong bactericidal ability but also kill tumor cells. For example, the antibacterial peptide D screened from silkworms has shown good application prospects and can be produced by genetic engineering technology. There are also a variety of active peptides in snake venom. A small peptide with 13 amino groups (INKAIAALAKKLL) is isolated from snake venom, which has strong bactericidal ability against G+ and G- bacteria.

6. Peptides for cardiovascular disease


Many plant Chinese medicines have the effects of lowering blood pressure, lowering blood lipids, and dissolving thrombosis. They can be used not only as medicines, but also as health foods. However, due to its composition, it cannot be determined. Its application is greatly restricted. Many active ingredients have been found to be small molecular peptides. For example, the active peptides processed and isolated from soybeans by Chinese scientists can be directly absorbed through the small intestine, which can prevent thrombosis, high blood pressure and hyperlipidemia, delay aging, and improve body tumor power. . Many small peptides used for cardiovascular diseases have also been isolated from ginseng, tea, ginkgo leaves and other plants.

7. Other small medicinal peptides


In addition to small peptide drugs that have made great progress in the above-mentioned aspects, some progress has also been made in many other fields. For example, Stiernberg et al. found that a synthetic peptide (TP508) peptide can promote the regeneration of wound blood vessels and accelerate the healing of deep skin wounds. Pfister et al. found that a small peptide (RTR) 4 can prevent the infiltration of inflammatory cells in the cornea from alkali damage and inhibit the inflammatory response. Carron et al. confirmed that the two synthetic peptides they screened can inhibit the resorption of bone by osteoclasts.

8. Diagnostic peptides


The main application of polypeptides in diagnostic reagents is to detect antibodies against viruses, cells, mycoplasma, spirochetes and other microorganisms and parasites such as cysticercosis and trypanosoma. The specificity of polypeptide antigens is stronger than that of natural microorganisms or parasite protein antigens. It is easy to prepare, so the assembled detection reagent has low false negative rate and background reaction of the detection antibody, and is easy for clinical application. Antibody detection reagents assembled with peptide antigens include: A, B, C, G or hepatic virus, HIV, human cytomegalovirus, herpes simplex virus, rubella virus, Treponema pallidum, cysticercosis, trypanosoma, Lyme disease and Rheumatoid and so on. Most of the peptide antigens used are obtained from the natural protein analysis and screening of the corresponding pathogens, and some are new small peptides screened from the peptide library.


9. Peptide vaccine


Peptide vaccines, like nucleic acid vaccines, are currently one of the more important research aspects in the field of vaccine research. In particular, a lot of research has been done on viral peptide vaccines. At present, there are no ideal vaccines for the two viral diseases, AIDS and hepatitis C, which are extremely harmful to humans. The research results of nucleic acid vaccines and peptide vaccines are encouraging. In 1999, the US NIH announced two HIV-I virus peptide vaccines. The results of phase I clinical trials conducted on humans confirmed that the two peptides can stimulate the body to produce specific antibodies and specific cellular immunity, and have good safety. Tsinghua University in my country has also confirmed that a peptide in the HIV-I membrane protein has strong immunogenicity. Hepatitis C virus peptide vaccines also show good development prospects. Foreign scholars have screened general peptides from the hepatitis C virus (HCV) outer membrane protein E2, which can stimulate the body to produce protective antibodies. Research on peptide vaccines for other viruses (such as hepatitis A, measles, Sindbis virus, etc.) and peptide vaccines against tumors and contraception has also made great progress. For example, the American scholar NaZ et al. screened a small 12-amino acid peptide from the phage peptide library, which can specifically bind to human eggs and prevent the combination of sperm and eggs, and can be used as a contraceptive vaccine.

10. Peptide drug carrier


Polypeptide is used as a drug carrier, it can be used as a modifier of the drug carrier, and can also be used as the main component of the drug carrier. Law et al. designed the peptide segment connected by the protease breakpoint to self-assemble in a suitable solvent and coat the drug in the microsphere. When it encounters the targeted protease, the breakpoint is broken to achieve the targeted release of the drug. Peng Shiqi et al. used Arg-Gly-Asp-Ser (RGDS) tetrapeptide modified liposomes as drug carriers to guide thrombolysis. Using platelet fibrinogen (FG) receptor ligand RGDS peptide as a guiding homing device, coupled to liposomes encapsulating urinary hormone UK. The carrier and the drug are connected in the form of an acid-sensitive covalent bond, which can be biodegraded into the endogenous substance Glu in nature or in the human body, and it is not easy to produce accumulation and toxic side effects.

11. Tissue engineering materials


Some non-biologically active macromolecular peptides, such as polyaspartic acid, polylysine, polyglutamic acid, etc., have good biocompatibility, controllable biodegradation rate, modifiability, and design plasticity , Structure controllability and other advantages, has gradually become a new type of material with great application prospects in tissue engineering. Langer et al. prepared poly(lactic acid-lysine) and grafted RGD peptide to the -NH2 of lysine in the polymer, which effectively improved the cell adhesion ability on the polymer surface and overcome the inactive groups of the main chain. The obtained tissue engineering scaffold material is not only convenient for cell identification, but also can support cell growth

12. Polypeptide nutritional food


As a new type of health food or food additive, active peptide food has unique characteristics and functions. It also has many advantages in nutrition and has broad application prospects in the food industry.


13. Cosmetic peptides


Tripeptides are growth factors, tetrapeptides have anti-inflammatory effects, pentapeptides can promote collagen to increase skin thickness, hexapeptides are botulinum-like, can relax wrinkles, and nonapeptides can block melanin-stimulating hormone and have whitening effects. According to the current research results, the peptides used in cosmetics are mainly peptides within six amino acid residues. If the peptide chain exceeds six residues, the skin is not easy to absorb, so the number of amino acids that can be used clinically overlaps. high. In addition to a little clinical and basic research on pentapeptide (Matrixyl) and hexapeptide (Argireline), some new peptides, especially combination peptides, have a mystery in their efficacy.

Before the arrival of the new millennium, the WHO (World Health Organization) called for: "The biggest disease of mankind in the 21st century is lifestyle disease." Polypeptides will play a great role in improving and adjusting people's lifestyles. Perhaps one day in the future, we will take vitamin-added peptides in the morning to provide us with vigorous energy for our day's work; at noon, we will take comprehensive nutritional peptides with a simple working meal to balance our nutrition; face high fat, high protein, and high calories For a sumptuous dinner, we take fat-lowering and gastrointestinal-satisfying peptides, which not only solves our desire for delicious food, but also does not make us ignorant of restraint; people send down sleep peptides with milk before going to bed, which makes good dreams endless.

On holidays, when you exercise with your friends, take a little relaxing peptide to quickly relieve fatigue; face students who are nervous about preparing for exams, mother will give him a box of sweet chocolate peptide candies; net worms lingering in front of the computer, in your mouth Chewing on peptide chewing gum that can resist the radiation of the screen; for girls who love beauty, use peptide creams and facial masks to keep your youth and beauty; for young women who are charming and beautiful, anti-aging peptides can keep you strong; the autumn is high and refreshing on the Double Ninth Festival, senior citizens People (called the elderly in China) mouth-containing peptide ginseng tablets climb high and travel without breathing; a beautiful cup of passion peptide makes happy couples feel more happy... All this is not science fiction, but the world of peptides that is unfolding in front of you and me . In general, peptide drugs extracted from animal tissues will be gradually eliminated, and chemical synthesis and gene recombinant expression will become complementary methods of peptide drug production for a long time.