324
D. J. BELL
Pelvetia, and Macrocystis, all yield an acidic polysaccharide, fucoidin,
where the majority of the L-fucose units are esterified by sulfate (150).
The sugar is frequently a component of the carbohydrate moieties of
glycoproteins (102, 103), blood group substances (1Ö4) and also occurs
in the oligosaccharides of human milk (Section VI,B). It has been
found free (104a).
I. L-ARABINOSE
1. Free
Traces of the free sugar have been found in numerous situations
(cf. Section VII).
2. Combined
^Arabofuranose
Many polysaccharides of vegetable origin are partly or wholly composed of L-arabofuranose units. Arabans occur in crude "pectin" (151)
preparations from sugar beet (152), peanuts (Arachis hypogaea) (153),
and apples (154). Many xylans (see Chapter 8, this volume) contain
varying amounts of L-arabofuranose units attached to the main D-xylose
chains; gums (135, 136) are also partly composed of this sugar. The
blue-green alga Anabaena cylindrica (154) and the green alga Cladophora rupestris also contain combined L-arabinose.
3. Combined lu-Arabopyranose
L-Arabopyranose units have been detected as components of gums
from lemon, peach, cherry, and apple trees (155), from Virgilia (155a),
and from Acacia karroo (155b). In these gums the great majority of
the arabinose units have the furanose configuration. The disaccharide
vicianose (Section VI,B,2) also contains an L-arabopyranose unit.
J. D-ARABINOSE
The sugar has been found only combined in bacterial products (48a,
48b) and in the Caribbean sponge (48).
K. L-RHAMNOSE
L-Rhamnose is very widely distributed among plants and is found in
some bacterial products; in all these, isolated units derived from the
sugar occur in gums (97), glycosides, and a number of polysaccharides
of varying character. The sugar is not known to occur in animal tissues
nor does it form homopolysaccharides in the manner of most other
common sugars except D-ribose and 2-deoxy-D-ribose.
D. J. BELL
Pelvetia, and Macrocystis, all yield an acidic polysaccharide, fucoidin,
where the majority of the L-fucose units are esterified by sulfate (150).
The sugar is frequently a component of the carbohydrate moieties of
glycoproteins (102, 103), blood group substances (1Ö4) and also occurs
in the oligosaccharides of human milk (Section VI,B). It has been
found free (104a).
I. L-ARABINOSE
1. Free
Traces of the free sugar have been found in numerous situations
(cf. Section VII).
2. Combined
^Arabofuranose
Many polysaccharides of vegetable origin are partly or wholly composed of L-arabofuranose units. Arabans occur in crude "pectin" (151)
preparations from sugar beet (152), peanuts (Arachis hypogaea) (153),
and apples (154). Many xylans (see Chapter 8, this volume) contain
varying amounts of L-arabofuranose units attached to the main D-xylose
chains; gums (135, 136) are also partly composed of this sugar. The
blue-green alga Anabaena cylindrica (154) and the green alga Cladophora rupestris also contain combined L-arabinose.
3. Combined lu-Arabopyranose
L-Arabopyranose units have been detected as components of gums
from lemon, peach, cherry, and apple trees (155), from Virgilia (155a),
and from Acacia karroo (155b). In these gums the great majority of
the arabinose units have the furanose configuration. The disaccharide
vicianose (Section VI,B,2) also contains an L-arabopyranose unit.
J. D-ARABINOSE
The sugar has been found only combined in bacterial products (48a,
48b) and in the Caribbean sponge (48).
K. L-RHAMNOSE
L-Rhamnose is very widely distributed among plants and is found in
some bacterial products; in all these, isolated units derived from the
sugar occur in gums (97), glycosides, and a number of polysaccharides
of varying character. The sugar is not known to occur in animal tissues
nor does it form homopolysaccharides in the manner of most other
common sugars except D-ribose and 2-deoxy-D-ribose.