Peptide is a compound formed by connecting α-amino acids with peptide bonds. It is also an intermediate product of protein hydrolysis. Generally, the number of amino acids contained in a peptide is from two to nine. The peptide has many different names depending on the number of amino acids in the peptide. One compound formed by the dehydration. Condensation of two amino acid molecules is called two peptides. By analogy, there are three Peptides, all the way up to nonapeptides.
Compounds usually formed by the dehydration and condensation of 10 to 100 amino acid molecules are called peptides. Their molecular weight is less than 10,000 Da (Dalton). They can pass through semipermeable membranes and are not precipitated by trichloroacetic acid and ammonium sulfate. There are also literatures that refer to peptides composed of 2 to 10 amino acids as oligopeptides (small molecule peptides); peptides composed of 10 to 50 amino acids are called polypeptides; peptides composed of more than 50 amino acids are called proteins. In other words, Proteins are sometimes called peptides.
Classification of peptides
There are two types of peptides: biologically active peptides and synthetic peptides.
Types of peptides
Cytokine mimetic peptide
The use of known cytokine receptors to screen cytokine mimetic peptides from peptide libraries has become a hot research topic at home and abroad in recent years. Foreign peptides have been screened to simulate various growth factors such as human erythropoietin, human thrombopoietin, human growth hormone, human nerve growth factor and interleukin. The amino acid sequences of these simulated peptides are consistent with the amino acids of the corresponding cytokines. The sequences are different, but they have cytokine activity and have the advantage of small molecular weight. These cytokine mimetic peptides are in preclinical or clinical research stages.
Antibacterial active peptides
When insects are stimulated by the external environment, they produce a large number of cationic peptides with antibacterial activity. It have been screened out more than a hundred antibacterial peptides. 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 antimicrobial peptide D screened from silkworms shows good application prospects and can be produced using genetic engineering technology. There are also a variety of active peptides in snake venom. A small peptide of 13 amino acids (INKAIAALAKKLL) was isolated from snake venom, which has bactericidal ability against both G+ and G- bacteria.
Peptides for cardiovascular disease
Many plant-based traditional 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, because its active ingredients cannot be determined, its application is greatly limited. It has been found that many active ingredients are small molecule peptides. For example, the active peptides isolated from soybeans by Chinese scientists can be directly absorbed through the small intestine and can prevent and treat blood clots, hypertension and hyperlipidemia. They can also delay aging and improve the body’s anti-tumor resistance. ability. Many small peptides used for cardiovascular diseases have also been isolated from ginseng, tea, ginkgo leaves and other plants.
Other medicinal small peptides
In addition to making great progress in the above-mentioned major aspects, small peptide drugs have also made some progress in many other fields. For example, Stiernberg et al. found that a synthetic peptide (TP508) can promote the regeneration of blood vessels in wounds and accelerate the healing of deep skin wounds. Pfister et al. found that a small peptide (RTR) 4 can prevent the invasion of inflammatory cells in the alkali-damaged cornea and inhibit the inflammatory response. Carron et al. confirmed that the two synthetic peptides they screened can inhibit the reabsorption of bone by osteoclasts.
Diagnostic peptides
The most important use of peptides in diagnostic reagents is to use them as antigens to detect antibodies against viruses, cells, mycoplasma, spirochetes and other microorganisms, and parasites such as cysticercosis and trypanosomes. Polypeptide antigens are more specific than natural microbial or parasite protein antigens. Peptides is easy for clinical application because of it is easy to prepare, the assembled detection reagent has a low false negative rate and background reaction for detecting antibodies. Antibody detection reagents assembled with polypeptide antigens include: A, B, C, G or hepatitis viruses, HIV, human cytomegalovirus, herpes simplex virus, rubella virus, Treponema pallidum, cysticercosis, trypanosomes, Lyme disease and similar Rheumatism etc. Most of the peptide antigens used are obtained from the natural protein analysis and screening of the corresponding pathogens. Some are brand-new small peptides screened from the peptide library.
Effects of peptides on the human body
Active peptides mainly control the growth, development, immune regulation and metabolism of the human body. They are in a balanced state in the human body. If the active peptides are reduced, the functions of the human body will undergo important changes. For children, their growth and development will become slower. , or even stop, it will form dwarfs in the long run. For adults or the elderly, lack of active peptides will cause their own immunity to decline, metabolic disorders. It also cause endocrine disorders, causing various diseases, such as insomnia, weight loss, or edema. Since active peptides also act on the nervous system, the human body will become sluggish and the mind will no longer be smart. More importantly, the active peptides will decrease, which directly causes the gradual overall aging of various parts of the human body and causes various diseases.
The importance of peptides
Many active substances in the human body exist in the form of peptides. Peptides are involved in various fields of human hormones, nerves, cell growth and reproduction. Their importance lies in regulating the physiological functions of various systems and cells in the body, activating relevant enzyme systems in the body, promoting the permeability of intermediate metabolic membranes, or by controlling DNA transcription or Affects specific protein synthesis, ultimately producing specific physiological effects. Peptides are important substances involved in various cellular functions in the human body. It can be synthesized by cells and regulate their functional activities. Peptides act as neurotransmitters in the human body, transmitting messages.
Peptides can be used as transportation vehicles in the human body to transport various nutrients eaten by the human body. As well as various vitamins, biotin, calcium and trace elements beneficial to the human body, to various cells, organs and tissues of the human body. Peptide is an important physiological regulator of the human body. It can comprehensively regulate human physiological functions, enhance and exert human physiological activity, and has important biological functions. Peptides are very important to human cell activity, functional activities, and life existence. However, due to various factors, modern people have lost peptides in the human body, and the ability to synthesize peptides has been greatly weakened. Therefore, the modern human body lacks peptides and must supplement artificially synthesized peptides. Supplement peptides is to replenish activity, to replenish peptides is to replenish vitality, and to replenish peptides is Replenish life.
