PHOSPHATIDES

From Big Medical Encyclopedia

FOSFATYDY (a synonym phospholipids) — esters of polyatomic alcohol of glycerin or sphingosine with higher fatty acids and phosphoric acid. In structure F. also nitrogen-containing connections — sincaline, ethanolamine or serine enter. T. are found as a part of fabrics and zooblasts, plants and microorganisms both in a free look, and in the form of proteinaceous and lipidic complexes — lipoproteids (see) and proteolipids. T. are a part of a plasma membrane of a cell and membranes of cellular organellas (kernels, mitochondrions, a cytoplasmic reticulum, lysosomes, etc.) where lakes form a structural basis of a membrane — fosfatidny (fosfo lipidic) bisly (see Membranes biological).

Function F. in an organism it is diverse and up to the end it is not found out. T. or their certain representatives play an important role in ensuring constancy of structure and normal functioning of cellular membranes, activation of membrane and lysosomic enzymes (see), carrying out nervous impulses, fibrillation, course immunol. reactions, processes of proliferation of cells and an angenesis, electron transfer in a respiratory chain, absorption of fats and products of their splitting and resynthesis of lipids in a wall of intestines (see the Lipometabolism). At last, the special role belongs to F. in formation of lipo-proteidny and proteolipidny complexes. T. lipoproteids of a blood plasma participate in transport of triglycerides (see) and cholesterol (see), and the phosphatides of a letsitina which are a part of lipoproteids of high density (see) are substrate of the reaction catalyzed by le-tsitin:kholesterin (-ol) acyltransferase (KF 2.3.1.43), in the course the cut occurs etherification of cholesterol. The most part of ethers of cholesterol of a blood plasma is formed this way.

Insufficient receipt in an organism F. leads to heavy disbolism, development patol. states. Genetically caused disturbances of exchange F. sphingolipidoses are the reason of a number of hereditary diseases, such as different lipidoses (see), including (see).

Depending on what polyatomic alcohol participates in education F. — glycerin (see) or sphingosine (see), T. divide into two groups: glycerophosphatides (glitse-

rofosfolipida) and sfingofosfati-da (sfingofosfolipida).

Form a basis of glycerophosphatides fosfatidny to - you, containing, as a rule, in «-the provision of a molecule of glycerin the rest saturated and in r-situation — unsaturated fat to - you (see. Fatty acids). Depending on the nature of the nitrogen-containing connection attached to phosphoric to - those, glycerophosphatides, in turn, divide into fos-fatidilkholina (letsitina), phosphate go l ethanol amines (kephalins) and fos-fatidilserina. The composition of nek-ry glycerophosphatides — fosfatidil-inositols — instead of nitrogen-containing connection includes free of hexatomic alcohol of nitrogen inositol, or an inositol. Are close to glitserofosfa-tida of a fosfatidala (plasmalogens, or atsetalfosfatida), in a molecule to-rykh one of spirit groups of glycerin it is connected not with the rest fat to - you, and with the aldehyde corresponding to it forming hemiacetal group (see Plasmalogens).

The special group of glycerophosphatides is represented by difosfatidilgli-tserina, their molecule consists of two remains fosfatidny to - the t connected with glycerin the radio bonds formed between phosphatic groups fosfatidny to - t and and - alcohol groups of glycerin. One of representatives of difos-fatidilglitserin is the cardiolipin for the first time emitted from a cardiac muscle and which is a part of membranes of mitochondrions of all fabrics. It is still only F. with the established antigenic properties; cardiolipin is used as antigen in reaction of binding complement at diagnosis of syphilis (see Wasserman reaction).

Sfingofosfatida, to-rye call also sphingomyelins (see) because of their high content in myelin covers, incorporate amino alcohol sphingosine (more rare — a product of its recovery the diguide-rosfingozin) from the rest fat to - you, attached on an amino group; the rest phosphoric to - you is connected to hydroxylic group of a sfingozpn in molecules of sphingomyelins, the last is connected by radio communication with sincaline.

About a half of all F. an animal organism 20 — 40% — of phosphatidylethanolamines and other part — on other glitsero-and sfingofosfatida are the share of phosphatidylsincalines. Everywhere, where contain F., they are accompanied, as a rule, by cholesterol.

In a molecule F. it is possible to allocate the polar «head» formed phosphoric to - that and nitrogen-containing connection (at fosfatidilinozi-t — phosphoric to - that and an inositol) and bearing electric charge, and the fat and acid «tails» which are not bearing such charge. Thanks to it at F., unlike triglycerides, hydrophilic properties appear though in general hydrophobic properties prevail over hydrophilic.

T. represent badly crystallizing waxy substances. On air and on light they are oxidized. T. have the solubility characteristic of lipids (see), but unlike them form micelle structures (liposomes) in water. T. show properties of surface-active connections and are good emulsifiers (see Detergents).

At the person are richest with F. (in terms of dry weight) tissues of a brain and nerves — to 30%, their liver contains about 16%, kidneys — to 11%, heart — to 10%, skeletal muscles — apprx. 3%. In a blood plasma of the person concentration F. makes 110 — 275 mg! 100 ml, or 1,4 — 3,55 mmol! l (according to other data, 1,8 — 4,4 mmol! k), and ground mass F. is in structure of lipoproteids. Calculation of the general contents F. it is usually carried out on the basis of definition of lipidic phosphorus (see Blur a method).

In the USSR by the unified method of definition of the general F. in blood serum on the content of lipidic phosphorus the method, according to the Crimea F is. besiege trichloroacetic to-toi together with blood proteins and define phosphorus in the received deposit colorimetric (see Colorimetry) with ammonium molybdate. The method is offered in 1950 by A. Zilvers-mit and Davis (A. Davis). Normal the concentration of lipidic phosphorus determined by this method at adults makes 6,1 — 14,5 zhg/100 ml.

Biosynthesis F. most intensively proceeds in the liver, a wall of intestines, seed bubbles, ovaries lactating to a milk zhedeza, etc. it is carried out with the participation of a number of enzymes and coenzymes (ATP and tsitidpntrifosforny to - you, KOA). In addition to synthesis individual F. de novo in a liver occurs formation of phosphatidylsincalines by methylation fosfatidiletanolami-is new with the participation of S-adenozilmetio-nina: phosphatidylethanolamine +

38-adenoznlmetionin —» fosfatidil-sincaline + 38-adenozilgomotsistein.

At the decarboxylation of phospha-tidylserine proceeding with participation phosphatidylserine-dekarboksila-zy (KF 4.1.1.65) it is formed fosfa-tidnletanolamin.

In general for synthesis of phosphatidylsincalines large amounts of methionine (see) pl are required cared (see), requirement in to-rykh substantially becomes covered due to their receipt with food. At long food formation of phosphatidylsincalines in a liver is reduced by products with the low content of these connections owing to what fatty infiltration of a liver (develops see. Lipotropic substances).

Disintegration F. it is most intensive in intestines (splitting food F.) and a liver, at the same time products of partial or full hydrolysis F can be formed. The enzymes splitting F., call fos-fatidaza (phospholipases). Splitting F. can pass with the participation of several fosfatidaz (they are designated Latin letters: And,

In, With and D), each of to-rykh catalyzes a hydrolytic rupture of strictly certain communication (Rx and Pi2“ hydrocarbon radicals):


Shortcoming F. in an organism promotes also development of atherosclerosis (see), on the contrary, the increased contents detains them this process. The specified influence F. on development of atherosclerosis it is carried out through formation of lipoproteids of high density — the richest F. a class of lipoproteids, from those, to-rye are considered as antiaterogen-ny. The clinic calculated coefficient of F/H (phosphatides / holeste-rin). The size of this coefficient considerably decreased at atherosclerosis. Began to use more indicative coefficients, napr, the attitude of amount of cholesterol of atherogenous lipoproteids of low and very low density towards amount of cholesterol of lipoproteids of high density later.

The research of phospholipidic structure of a blood plasma is of great importance for establishment of the place of the fermental block at sphingolipidoses. Quantitative definition F. an amniotic fluid it is used for the purpose of clarification of a maturity of lungs of a fruit and risk of development of a syndrome of respiratory insufficiency. }' (la of holes of m and l N about about f at N to c and about N and r about in and a niya of lungs of the newborn shall be present at them surfactants (see) — the substances lowering surface intention in air cells and by that preventing their adhesion. Are a part of surfactants F. Formation of amounts of surfactants, necessary for normal life activity, in pulmonary fabric of a fruit comes to the end only by the end of pregnancy therefore for the premature child there is a danger of development of a syndrome of respiratory insufficiency. Low speed of formation of surfactants can take place and at normal durations of gestation. In such cases on the basis of determination of content of lecithin in an amniotic fluid or sizes of the relation of a letsitina: sfingomy l of Ina it is possible to predict a risk degree of emergence of respiratory insufficiency till the birth of the child. Low content of lecithin or low size of the relation of a letsitina: (less than 1,8) in an amniotic fluid at the end of pregnancy points out sphingomyelins danger of developing of asphyxia at the newborn (see Asphyxia of a fruit and the newborn) and demands acceptance of preventive measures.

To Bibliogrkrepa E. M. Lipids of cellular membranes, JI., 1981; The Guide to clinical laboratory diagnosis, under the editorship of V. V. Menshikov, e. 229, M., 1982; Whyte A., etc. Fundamentals of biochemistry, the lane with English, t. 1 — 2, M., 1981; Form and function of phospholipids, ed. by R. M. G. Dawson, Amsterdam — N. Y., 1973; Holub B. J. a. Kuksis A. Metabolism of molecular species of diacyl-glycerophospholipids, Advanc. Lipid Res., v. 16, p. 1, 1978. A. H. Klimov.

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