CEREBROSIDES

From Big Medical Encyclopedia

TsEREBROZYDY — the lipoid substances which are contained in significant amounts in nervous tissue and in smaller quantities in other fabrics of an animal organism; are found also in seeds of nek-ry plants and mushrooms. Genetically caused disturbances of exchange of C., observed at lipidoses (see), are the reason of serious hereditary diseases (see),

sphingosine C. from tissues of animals and the person are constructed of amino alcohol of sphingosine, or a sfingenin, is more rare — the diguide-rosfingozina, or the sfinganina (see Sphingosines), carbohydrate of a galactose (see) and fat to - you, a molecule a cut consists, as a rule, of 24 carbon atoms (see. Fatty acids). As C. contain both sphingosine, and sugar, they can be carried at the same time to sphingolipids (see) and to glycolipids (see). In rare instances in structure of C. instead of a galactose glucose enters (see). Therefore sometimes to emphasize

structure of C., use the terms «hectare lactocerebrosides», «gliko-, or glucocerebrosides». Ethers C. with a chamois to - that on spirit group at the 3rd carbon atom of a galactose call sulfocerebroside-mi, or sulfatides (see).

From a brain 4 representatives of C are allocated and characterized., differing only in the nature fat to - you. It is kerasin (lignoceric to - that), tserebron, or phrenosin (the guide-roksilignotserinovaya, or cerebronic to - that), nervone (an unsaturated homolog lignoceric to - you — nervonovy to - that) and oxynervone (hydroxy-nervonovaya to - that). In addition to the mentioned C., in a brain of animals small amounts of C are found., to-rykh are a part palmitic and stearin to - you.



Fig. 2. The scheme of biosynthesis of cerebrosides through N-acylation and a glycosylation of sphingosine: R is the hydrocarbon radical, UDF — uridinediphosphate, Udfgal — an uridindifosfatgalaktoza.


C. represent white amorphous matters, but can be received also in a crystal look. Like fats (see), C. are water-insoluble, but unlike them are insoluble also in nek-ry organic solvents (ether, acetone, cold alcohol). C. are well dissolved in pyridine and in mix of chloroform with methyl alcohol, and also in hot alcohol. At alkaline hydrolysis of C. from their molecules it is chipped off fat to - that and there is a water soluble galactoside of sphingosine called psikhoziny. On the contrary, at soft acid hydrolysis (in acetic to - that) from a molecule C. the galactose is chipped off and there is a water-insoluble fat and acid amide of sphingosine called by ceramide. At hydrolysis in rigid conditions (in the presence of strong to - t) C. are split on sphingosine, a galactose and fat to - that.

The highest content of C. note in nervous tissue. The brain of adult mammals contains 13 — 22 mg of C. on 1 g of fabric. Part C. in nervous tissue is in a type of sulfocerebrosides.

Value C. for a human body is studied insufficiently. Because ground mass of C. is in white matter of a brain, assume that C. on an equal basis with cholesterol (see) and with fingo myelins (see) are typical «obkla-dochny», or myelin lipids. Preferential


zation of C of a locale. in miyeltsnovy covers, existence in their molecules long-chain fat to - t and extremely slow speed of updating C. confirm, apparently, participation of C. in ensuring stability and durability of myelin educations. Along with it participation of C is established. in such processes as activation of membrane enzymes, transport of ions (see) through membranes (see Membranes biological), superficial reception (see), to them-munol. reactions, etc.

In a brain of the person and animals the fermental systems participating in biosynthesis and disintegration of C are found. Synthesis of C. can pass in two ways; at one of them initial reaction is the glycosylation of sphingosine accompanied with N-acylation, and at the friend — N - acylation of sphingosine precedes a glycosylation. In both cases the glycosylation is carried out by means of an uridindi-fosfatgalaktoza (Udfgal), and acylation — with the participation of corresponding atsil-KOA. As an intermediate product at the first way of synthesis of C. it is formed psikhozin, and at the second — ceramide (fig. 2).

Disintegration of C. it is carried out hydrolytic and catalyzed by the corresponding hydrolases (see); as the first products of enzymic hydrolysis of C. ceramide and a galactose are formed.

Genetically caused disturbances of exchange of C. observe at lipidoses (see), napr, at a disease to Gosha (see Gosha a disease) when one of C. — kerasin — is laid in tissue of a spleen and liver, and an overwhelming part of a galactose in kerasin is replaced with glucose. At other types of lipidoses disturbance of exchange of sulfatides is noted: extremely high adjournment of sulfatides in c is characteristic of a family metachromatic leukodystrophy of Greenfield — Sholtsa. N of page, kidneys, a liver, a retina of eyes and nek-ry other bodies, and for Krabbe's disease, on the contrary, at the increased maintenance of C. and glycero-phosphatides almost total absence of sulfatides in a brain is characteristic (see Leykodist of a raffia).

Bibliography: To r e p with E. M. Lipids to a kla

of exact membranes, D., 1981; Lipids and lipidoses, ed. by G. Schettler, B. u. a., 1967.

A. H. Klimov.

Яндекс.Метрика