What is the synthesis of lysine

Lysine(Lys) is assigned to the 21 L-amino acids that are regularly incorporated into proteins. For this reason, lysine is called proteinogenic and is essential for the biosynthesis of proteins and the maintenance of muscle and connective tissue. A deficit of lysine can impair protein biosynthesis (new formation of proteins) [1].

According to its chemical structure and composition, lysine is one of the basic amino acids, to whom too Histidine and Arginine counting. Since all three amino acids consist of six carbon atoms and one basic group, they are called Hexon bases designated.
In the case of lysine, the free amino group (NH2) in the side chain as a base, especially if the pH value is too low or acidic. If that is the case, take it free NH2-Group of lysine protons (H +) from the environment and will to NH3+. By binding protons, lysine increases the pH value of the environment and at the same time receives a positive charge.
In this way, the basic amino acids maintain the pH value in the extra- and intracellular space of the organism [10].

Lysine is not produced by the human body itself and is therefore essential (vital). In addition to lysine, eight other amino acids are considered essential, all of which must be taken in with food and cannot be replaced by other amino acids [10].
While seven of the essential amino acids in the intermediate metabolism can be formed from their corresponding alpha-keto acids through a transamination reaction, this is the case with lysine and Threonine not the case. These are irreversibly transaminated and consequently referred to as the actual essential amino acids [4].

Digestion and Intestinal Absorption

The partial hydrolysis of food proteins begins in the stomach. Important substances for protein digestion are secreted from various cells of the gastric mucosa. The main cells produce pepsinogen, the precursor of the protein-splitting enzyme pepsin. The parietal or parietal cells produce gastric acid (HCl), which promotes the conversion of pepsinogen to pepsin. In addition, HCl lowers the pH value in the stomach, which increases pepsin activity.

Pepsin breaks down lysine-rich protein into low-molecular-weight breakdown products such as poly- and oligopeptides. Good natural sources of lysine include whey, egg, meat, soy, wheat germ, lentil and amaranth protein, as well as casein. In addition, the cooking water from potatoes has high levels of lysine, as the amino acid is detached from the potato protein by the action of heat [1].

The soluble poly- and oligopeptides then reach the small intestine, the location of the main ones Proteolysis (Protein digestion). Be in the acinar cells of the pancreas (pancreas) Proteases (protein-splitting enzymes). The proteases are first synthesized and secreted as zymogens - inactive precursors. The zymogens are only activated in the small intestine Enteropeptidases, Calcium and the digestive enzyme Trypsin.
Enteropeptidases are enzymes that are formed by the enterocytes (cells of the intestinal mucosa) and released when food protein arrives.
Together with calcium, they lead to the conversion of trypsinogen to trypsin in the intestinal lumen, which in turn is responsible for the activation of other zymogens derived from the pancreatic secretion [3, 5, 8, 10, 23, 24].

The most important proteases are the endo- and exopeptidases. Endopeptidasessuch as trypsin, chymotrypsin, elastase, collagenase and enteropeptidase, split proteins and polypeptides inside the molecules, which increases the terminal vulnerability of the proteins. Exopeptidasessuch as carboxypeptidase A and B as well as amino and dipeptidases attack the peptide bonds of the chain end and can specifically split off certain amino acids from the carboxy or amino end of the protein molecules. They are correspondingly referred to as carboxy or aminopeptidases. Endo- and exopeptidases complement each other due to their different substrate specificity when cleaving proteins and polypeptides.

Through the Endopeptidase trypsin the basic amino acids lysine, arginine, histidine, ornithine and cystine are specifically released at the C-terminal end of the peptide chain. Lysine is then located at the end of the protein and is therefore accessible for cleavage Carboxypeptidase B. This exopeptidase only cleaves basic amino acids from oligopeptides [3, 5, 23].

At the end of protein digestion, lysine is either available as a free amino acid or bound to other amino acids in the form of di- and tripeptides [10].
In its free, unbound form, lysine is mainly actively and electrogenically absorbed in sodium cotransport into the enterocytes (mucosal cells) of the small intestine. The driving force of this process is a cell level directed sodium gradient, which is maintained with the help of the sodium / potassium ATPase.
If lysine is still part of di- or tripeptides, these are transported into the enterocytes against a concentration gradient in the H + cotransport. Intracellularly, the peptides are broken down by amino- and dipeptidases into free amino acids, including lysine.
Lysine leaves the enterocytes via various transport systems along the concentration gradient and is transported to the liver via the portal blood.

The intestinal absorption of lysine is almost complete at almost 100%. However, there are differences in the rate of absorption. Essential amino acids such as lysine, isoleucine, valine, phenylalanine, tryptophan and methionine are absorbed much faster than non-essential amino acids. Compared to the neutral amino acids, the amino acids with a basic side group are taken up into the enterocytes at a significantly slower rate [3, 5, 8, 10, 23, 24].

The splitting of food proteins and endogenous proteins into smaller breakdown products is not only important for the uptake of peptides and amino acids in the enterocytes, but also serves to resolve the alien character of the protein molecule and to exclude immunological reactions [10].

literature

  1. Arndt K, Albers T: Handbook Protein and Amino Acids. 184-188. 2nd edition Novagenics Verlag 2004
  2. Atar D, Spiess M, Mandinova A, Cierpka H, ​​Noll G, Lüscher TF: Carnitine - from cellular mechanism to potential clinical applications in heart disease. Eur J Clin Invest. 1997 Dec; 27 (12): 973-6.
  3. Bender DA: Intoduction to Nutrition and Metabolism. Taylor and Francis Ltd., London, reprinted September 2007
  4. Biesalski HK, Grimm P: Pocket Atlas of Nutrition. 112, 124. Georg Thieme Verlag, Stuttgart / New York, 1999
  5. Bowman BA, Russel RM (eds.): Present Knowledge in Nutrition. International Life Sciences Institute, Washington, D.C .; 9th ed .; 2006
  6. Brainum J: Amino Acids - the protein / growth connection. Ironman 7: 114; 1988
  7. Brass EP, Hiatt WR: The role of carnitine and carnitine supplementation during exercise in man and in individuals with special needs. J Am Coll Nutr. 1998 Jun; 17 (3): 207-15.
  8. Daniel H: Molecular and integrative physiology of intestinal peptide transport. Annu Rev Physiol. 2004; 66: 361-84.
  9. Gürtler AK, Löster H: Carnitine and its importance in the pathogenesis and therapy of cardiovascular diseases. Ponte Press, Bochum; 1996
  10. Hahn A, Ströhle A, Wolters M: Nutrition - Physiological Basics, Prevention, Therapy. 46-65. Wissenschaftliche Verlagsgesellschaft mbH, Stuttgart, 2006
  11. Lee WH: Amazing amino acids. Keats Publishing Inc .; P.7; 1984
  12. Mc Garry JD, Brown NF: The mitochondrial carnitine palmitoyltransferase system. From concept to molecular analysis. Eur J Biochem. 1997 Feb 15; 244 (1): 1-14.
  13. Meijer AJ: Nitrogen metabolism and ornithine cycle function. Physiol Rev. 1990 Jul; 70 (3): 701-48.
  14. Merck KG: Data sheet L-lysine monohydrochloride for biochemical purposes. CD-ROM version; 64271 Darmstadt; 1999 / 2D
  15. Luppa D: L-Carnitine losses through urine and sweat in athletes dependence of energy expenditure during training. In: Seim H, Löster H (eds.) Carnitine - Pathobiochemical basics and clinical application. Ponte Press, Bochum: 278-279; 1996
  16. Luppa D: Compensating for load-related L-carnitine losses with food protects against various functional disorders. Klin Sportmed: 61-67; 2002
  17. Luppa D: Participation of L-carnitine in the regulation of fat and carbohydrate metabolism. KCS 2004, 5 (1): 25-34
  18. Niestroj I: Practice of Orthomolecular Medicine. 48, 366, 437. Hippokrates Verlag, Stuttgart; 2000
  19. Rath M, Niedzwiecki A: Nutritional supplement program halts progression of early coronary atherosclerosis documented by ultrafast computed tomography. Journal of Applied Nutrition 48: 68-78; 1996
  20. Regitz-Zagrosek V, Fleck E: Myocardial carnitine deficiency in human cardiopathia. In: De Jong JW, Ferrari R (eds.) The carnitine-system - A new therapeutic approach to cardiovascular diseases. Kluwer Academic Publishers, Dordrecht: 145-166; 1995
  21. Scholte HR, Rodrigues Pereira R, De Jonge PC, Luyt-Houwen IEM, Verduin MHM, Ross JD: Primary carnitine deficiency. J Clin Chem Clin Biochem 28: 351-357; 1990
  22. Schmidt-Sommerfeld E, Penn E: Carnitine Deficiency. Monthly Pediatrics 134: 224-231; 1986
  23. Shils ME, Olson JA, Shike M, Rossi AC (Eds.): Modern Nutrition in Health and Disease. Williams and Wilkons, London, Munich; 10th ed. 2005
  24. Wu G: Intestinal mucosal amino acid catabolism. J Nutr. 1998 Aug; 128 (8): 1249-52.
  25. Zimmermann M: Micronutrients in Medicine. 189. Karl F. Haug Verlag, Stuttgart; 2003

 


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