From Big Medical Encyclopedia

GALACTANS — polysaccharides, molecules to-rykh are constructed preferential of the remains of D-or L-galactose. Along with the remains of a galactose in G. the remains of an angidrogalaktoza often meet, to-rye either metilirovana, or the remains of other sugars, napr, pentoses, pectine sugars can be sulphated.

Are eurysynusic in the nature, especially in plants, but meet also in animal organisms. Certain representatives of galactans, such as agarose and karagenin, have practical value, are used in bacteriology, the pharmaceutical, food and textile industry (see the Agar, the Agar beef-extract).

One of the most widespread is G. which is a part of impurity of pectin (see. Pectic substances ) and constructed of the remains of a D-galactose connected beta 1,4 - glycosidic linkages:

Hemicellulose coniferous, especially to wood of a larch, contains soluble arabinogalactan. It represents substance with branched structure, a basis a cut the remains of a D-galactose connected β-1,3-and β-1,6-(perhaps, and β-1,4-) are bonds; the remains of L-arabinofuranozy in such G.'s molecule are endgroups.

Agarose (a component of an agar) allocated from lavers has a linear structure and contains the remains of a D-galactose and 3,6-angidro-L-galactose connected serially β-1,4-and α-1,3-svyazyam; treats G. also porfiran — the sulphated G. from an alga of Porphyra umbilicalis, consisting of the alternating remains of D-and L-galactose, and the remains of a D-galactose at the sixth C-atom of a metilirovana, and the remains of a L-galactose in the same situation are sulphated. From an alga of Chondrus crispus L-karagenin similar to agarose, but differing from it in existence of a 3,6-angidro-D-galactose (instead of a 3,6-angidro-L-galactose) and bearing at C is allocated 4 D-galaktoznykh of the remains sulphatic groups.

Of complex dichotomizing structure is allocated from a snail (Helix pomatia).

It is allocated also from lungs of cattle. It has the expressed antigenic properties — forms precipitated calcium superphosphate with polysaccharide of a pneumococcus like XIV.

See also Galactose , Polysaccharides .

Bibliography: Kochetkov N. K., etc. Chemistry of carbohydrates, M., 1967.

B. N. Stepanenko.