GALACTOSE

From Big Medical Encyclopedia

GALACTOSE (grech, gala, galaktos milk; synonym tserebroza; With 6 H 12 O 6 ) — a monosaccharide from group of hexoses, the isomer of glucose differing from it in a spatial relationship of atomic groups at the fourth C-atom. Is an important component of food of the baby, is a part of disaccharide of lactose, to-ry represents the main carbohydrate of milk. Pier. weight 180,16. As all monosaccharides, it is characterized by existence of D-and L-isomers. Exists in acyclic (1) and cyclic (2) forms.

The D-galactose represents crystals, t ° pl 168 °; 1 part G. at t°0 ° is dissolved in 9,7 parts of water, [a]D is equal +80,2 °. The galactose recovers solution of Felinga (see. Carbohydrates ). G. in dicarbonic mucic to - that, low solubility in water is oxidized (see. Hexonic acids). This reaction serves for detection and quantitative definition of G. and its nek-ry derivatives. Specific microchemical definition of G. is made by means of enzyme of a galaktozooksidaza (KF 1.1.3.9).

It is eurysynusic in the nature in the form of oligosaccharides: lactoses, from a cut usually receive G. by hydrolysis, trisaccharide of raffinose, a tetrasakharid of stachyose, and also in the form of glycosides (an idein, Merthyllinum, a ksantoramnin, digitonin). Is a part of cerebrosides of a brain (from here it before the used name — a tserebroza) and complex glycoconjugates — glycoproteins, glycolipids and nek-ry mucopolysaccharides (glikozaminoglikan), and also the highest polysaccharides (an agar, arabic gum, many vegetable adhesives and slime). Crystal G. was found in berries of an ivy.

Disturbances of exchange At the person lead to development of a serious illness. Genetically caused disturbance of utilization of G. caused by defect in synthesis of the enzymes participating in its transformations conducts to galactosemia (see). Such enzymes are the hectare of laktozo-1-fosfaturidililtransferaza (KF 2.7.7.10), a galaktokinaz (KF 2.7.1.6), etc. Characteristic wedge. display of a galactosemia is bystry development of a cataract. Emergence of a cataract at early age [according to Gitzelmann, 1967] is caused by insufficiency of hectare of a lactokinase — the enzyme catalyzing transfer of phosphate from ATP on G. with education alpha D - galaktozo-1-phosphate (D-galaktozamin can be substrate in this reaction along with G.).

After inclusion in food of milk at people with such disease G.'s maintenance in blood (it is normal of it quantity in blood slightly) sharply increases and in the increased quantities it is formed galaktit. Accumulation in crystalline lenses can lead it to formation of a cataract owing to excessive hydration and disturbance of electrolytic balance. Tolerance to G. at the people having diabetes is close to that at healthy people.

See also Galactans , Hexoses , Carbohydrates .


Bibliography: Kochetkov N. K. y d river. Chemistry of carbohydrates, page 33, etc., M., 1967; Stepanenko B. N. Carbohydrates, Progress in studying of a structure and metabolism, page 29, etc., M., 1968; Harris G. Fundamentals of biochemical genetics of the person, the lane with English, page 158, M., 1973; The carbohydrates, chemistry and biochemistry, ed. by W. Pigman, v. 1A — 2A a. 2B, N. Y. — L., 19 70 —19 72.

B. H. Stepanenko.

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