Phosphatidylserine
Phosphatidylserine (abbreviated Ptd-L-Ser or PS ) is a phospholipid and part of biological membranes. It plays a key role in cell communication, especially in programmed cell death ( apoptosis ).
structure
PS is a phospholipid (more precisely a glycerophospholipid ). It consists of a glycerine that is linked to two fatty acids on the first and second carbon atoms via an ester bond and to a serine on the third carbon atom via a phosphodiester bond .
Depending on whether the PS is of vegetable or animal origin, it differs in its fatty acid composition.
Biological function
Cell communication
PS is kept active in the inner (cytosolic) monolayer of the cell membrane by the enzyme flippase . However, if the cell does apoptosis, it is also found in the outer monolayer. The scramblase enzyme catalyzes the rapid exchange between both sides of the cell membrane. If PS is found in the outer (extracellular) monolayer, it serves macrophages as a signal for phagocytosis .
Blood clotting
PS plays a role in blood clotting . When platelets on an injured blood vessel are activated by collagen and thrombin , there is a change in PS and other negatively charged phospholipids to the outer monolayer of the platelet membrane. This surface is used for the association of coagulation factors, especially the tissue factor (= thromboplastin) and factor VII . This makes the coagulation cascade easier: factor X is activated and ultimately thrombin is formed.
The Scott syndrome is clotting disorder in which the transport of PS is defective from the inner to the outer monolayer of the platelet membrane. Due to the reduced synthesis of thrombin, there is a slight coagulation disorder.
biosynthesis
PS is produced in the human organism from phosphatidylethanolamine . Here, ethanolamine against serine replaced. This reaction is catalyzed by the enzyme phosphatidylserine synthase , which is located in the mitochondria-associated ER membrane (MAM). This enzyme can also catalyze the reverse reaction, i.e. the conversion of phosphatidylserine to phosphatidylethanolamine.
Occurrence in food
The daily intake of PS through food is estimated at around 130 mg in Western countries. PS is found in meat and fish. Only small amounts are found in dairy products or vegetables (with the exception of white beans).
Table 1. PS content in various foods.
| food | PS content in mg / 100 g |
|---|---|
| Bovine brain | 713 |
| Atlantic mackerel | 480 |
| Chicken heart | 414 |
| Atlantic herring | 360 |
| eel | 335 |
| Offal (average) | 305 |
| Pork spleen | 239 |
| Pig kidney | 218 |
| tuna | 194 |
| Chicken thighs (skin-on, boneless) | 134 |
| Chicken liver | 123 |
| White beans | 107 |
| Sand gape clam | 87 |
| Chicken breast (skin-on) | 85 |
| Mullet | 76 |
| calf | 72 |
| Beef | 69 |
| pig | 57 |
| Pork liver | 50 |
| Turkey leg (skin and bone) | 50 |
| Turkey breast (skinless) | 45 |
| Crayfish | 40 |
| Octopus | 31 |
| Atlantic cod | 28 |
| Anchovies | 25th |
| Whole grain barley | 20th |
| hake | 17th |
| sardine | 16 |
| Trout | 14th |
| Rice (unpolished) | 3 |
| carrot | 2 |
| Sheep milk | 2 |
| Cow's milk (3.5% fat) | 1 |
| potato | 1 |
Individual evidence
- ^ David Nelson, Michael Cox: Lehninger Principles of biochemistry , 5th edition, WH Freeman and company ,, ISBN 9781429208925 , p. 350.
- ↑ Nutrition and Allergies EFSA Panel on Dietetic Products: Scientific Opinion on the substantiation of health claims related to phosphatidyl serine (ID 552, 711, 734, 1632, 1927) pursuant to Article 13 (1) of Regulation (EC) No 1924/2006 . In: EFSA Journal . 8, No. 10, October 1, 2010, ISSN 1831-4732 , p. 1749. doi : 10.2903 / j.efsa.2010.1749 .
- ↑ B. Verhoven, RA Schlegel, Williamson P: Mechanisms of phosphatidylserine exposure, a phagocyte recognition signal, on apoptotic T lymphocytes . In: Journal of Experimental Medicine . 182, No. 5, November 1, 1995, pp. 1597-601. doi : 10.1084 / jem.182.5.1597 . PMID 7595231 . PMC 2192221 (free full text). Retrieved August 23, 2014.
- ↑ BR Lentz: Exposure of platelet membrane phosphatidylserine regulates blood coagulation . In: Prog Lipid Res . 42, No. 5, September 2003, pp. 423-438. doi : 10.1016 / s0163-7827 (03) 00025-0 . PMID 12814644 .
- ↑ Zwaal FA, Comfurius P, Bevers EM. Scott syndrome, a bleeding disorder caused by defective scrambling of membrane phospholipids . Biochem Bioph Acta 2004; 1636: 119-128
- ↑ Weiss HJ. Scott syndrome: a disorder of platelet coagulant activity (PCA). Sem Hemat 1994; 31: 312-319
- ^ Joachim Rassow , Karin Hauser, Roland Netzker, Rainer Deutzmann: Dual Biochemistry Series (4th edition). Thieme. P. 352. ISBN 978-3-13-125354-5
- ↑ Souci SW, Expert E, Kraut H: Food Composition and Nutrition Tables. Medpharm Scientific Publishers Stuttgart . 2008.