Content
Is called peptide bonds to a specific type of link between one amino acid and another, which takes place through an amino group (-NH2) in the first amino acid and a carboxyl group (-COOH) in the second, producing a CO-NH covalent bond and releasing a water molecule.
In this way a new molecule called peptide and that will be named after both amino acids. Thus, the peptide bond between a molecule of to the girl (provided by the NH- terminal) and another from serine (which provides the -CO terminal) will be named an alanyl-serine peptide.
This is one of the forms of bonding that allow amino acids to be joined (by dehydration) to produce more complex structures (polypeptides), since, once the bond is obtained, it is possible to continue joining amino acids through the same process, starting from the free hydroxyl group. It is an extremely common procedure in living beings.
Properties
These types of links have certain characteristics. For example, the established link is simple, but shorter: with characteristics of a double bond, how to stabilize by resonance. The latter prevents free turns around the bond (something common in this type of bond), giving the peptide an inevitable flat structure.
Similarly, peptide bonds can be degraded or broken by hydrolysis (addition of water), releasing an amount of energy in a tremendously slow process. This can be accelerated in the presence of catalysts acidic, basic or enzymatic.
Examples of peptide bonds
Any peptide is a perfect example of peptide bonds, as they are the result of this type of amino acid joining. Here are some of the most important:
- Bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg). Composed of nine amino acids, this peptide is a drug that produces vasodilation and a drop in blood pressure, which is why it is used to treat hypertensive patients.
- Oxytocin (Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly-NH2). Hormone produced by the hypothalamus and that fulfills neuromoderating functions of the central nervous system and a vital role in the preparation of the female cervix during childbirth and of the breasts during lactation.
- Glucagon (NH2-His-Ser-Gln-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Lys-Tyr-Leu-Asp-Ser-Arg-Arg-Ala-Gln-Asp-Phe-Val- Gln-Trp-Leu-Met-Asn-Thr-COOH). Peptide hormone of 29 amino acids, which is synthesized in the pancreas and is involved in the metabolism of sugars.
- Glutathione (γ-glutamyl-L-cysteinylglycine). Tripeptide of three amino acids: cysteine, glutamate and glycine, is the main cellular antioxidant, which protects them from free radicals and peroxides.
- Vasopressin (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2). Segregated by the hypothalamus, it controls the reabsorption of water molecules from the urine, increasing their concentration and plays a key role as a blood homeostatic regulator. It is a nine amino acid hormone.
- Insulin. Polypeptide hormone made up of 51 amino acids, secreted by the pancreas to regulate the cycle of sugars in the blood.
- Prolactin. Peptide hormone that stimulates the production of milk in the maternal breasts. It is made up of a sequence of 198 amino acids.
- Leptin. Another peptide hormone that suppresses the feeling of hunger, and is composed of a chain of 167 amino acids.
- Gastrine. This peptide hormone regulates the production of gastric juices in the stomach. It is made up of 14 amino acids.
- Pepsin. Hormone composed of 326 amino acids long, responsible for regulating the processes of digestion and absorption of food.
