What is a peptide? It is a class of compounds whose molecular structure is between amino acids and proteins. It is composed of amino acids, but it is different from protein and belongs to the intermediate substance between them. Compounds in which amino acids can be connected to each other by peptide bonds are called peptides. A peptide containing less than 10 amino acids is called an oligopeptide, and a peptide with more than 10 amino acids is called a polypeptide, and a peptide with more than 50 amino acids is called a protein. Polypeptide has high biological activity, it can regulate various physiological activities and biochemical reactions. Up to now, people have discovered and isolated more than 100 kinds of peptides that exist in the human body. The research and utilization of peptides has shown an unprecedented prosperity in the world.
There are 5 types of peptides:
1. 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. Abroad, human erythropoietin, human thrombopoietin, human growth hormone, human nerve growth factor, interleukin and other growth factor mimic peptides have been screened. The amino acid sequence of these mimic peptides and the amino acids of their corresponding cytokines The sequence is different, but it has cytokine activity and has the advantage of small molecular weight. These cytokine mimetic peptides are in the stage of preclinical or clinical research.
2. Antibacterial active peptides
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 many active peptides in snake venom. A small peptide of 13 amino acids (INKAIAALAKKLL) is isolated from snake venom, which has strong bactericidal ability against G+ and G- bacteria.
3. Polypeptides for cardiovascular diseases
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 active ingredients, 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 anti-tumor force. Many small peptides used for cardiovascular diseases have also been isolated from ginseng, tea, ginkgo leaves and other plants.
4. 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.
5. 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 hepatitis 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.