338
D. J. BELL
For example, as recently as 1934 it has been stated that lactose "has not
been encountered in the plant kingdom" (231). Nonetheless, it was isolated in 1871 from ripe fruits of Achras sapota L. (232), in which its
occurrence was adequately confirmed in 1958 (233). Its reported detection in flowers of Forsythia (234) has been disproved.
During the past few years the presence in human milk of a number
of interesting oligosaccharides has come to light. These are either present
only in trace amounts or absent from certain other milks, notably that of
the cow, ewe, and goat. Nonruminant milks, of the cat, monkey, dog,
rabbit, mare, and sow, are richer in these lactose derivatives. The
original literature has been reviewed (235) and should be consulted
for details of this interesting collaboration between pediatricians in the
United States and chemists in Germany. The human milk oligosaccharides, which contain units derived from L-fucose and N-acetyl-D-glucosamine, are listed in Table IV.
Free lactose is found in the urine of lactating women (235a); as far
as other mammals are concerned, the writer can find references only to
the lactating cow (235b). It would be interesting to know whether the
unfortunate condition of gynecomastia in men is accompanied by
lactosuria.
2. Other Reducing Oligosaccharides
In this section consideration will be confined to substances other
than lactose and its derivatives, which have been definitely identified in
tissues or products of biological origin. A number of di- and higher
saccharides have been found in small amounts; as has been already
stated these substances are obviously metabolic intermediates in the
hydrolytic fusion of larger molecules or in the anabolic production of
more complicated carbohydrates. Little is known of the existence of
these processes although a few enzymes with transglycosylating activity
have been found, for example, the plant "D -enzyme" of Rees, the bacterial "amylomaltase" of Monod and Torriani, and the rat liver enzyme
of M. R. Stetten (235c).
The remainder of the reducing saccharides to be described in this
section are derived from "typical glycosides." A number of di- and
higher saccharides occur, chiefly in steroid glycosides, in which the
modes of combination of the monosaccharide units are not yet established; these substances are therefore omitted. Di- and higher saccharides obtained synthetically or by controlled hydrolysis of polysaccharides are likewise not described.
Table V summarizes the main bulk of the natural oligosaccharides.
D. J. BELL
For example, as recently as 1934 it has been stated that lactose "has not
been encountered in the plant kingdom" (231). Nonetheless, it was isolated in 1871 from ripe fruits of Achras sapota L. (232), in which its
occurrence was adequately confirmed in 1958 (233). Its reported detection in flowers of Forsythia (234) has been disproved.
During the past few years the presence in human milk of a number
of interesting oligosaccharides has come to light. These are either present
only in trace amounts or absent from certain other milks, notably that of
the cow, ewe, and goat. Nonruminant milks, of the cat, monkey, dog,
rabbit, mare, and sow, are richer in these lactose derivatives. The
original literature has been reviewed (235) and should be consulted
for details of this interesting collaboration between pediatricians in the
United States and chemists in Germany. The human milk oligosaccharides, which contain units derived from L-fucose and N-acetyl-D-glucosamine, are listed in Table IV.
Free lactose is found in the urine of lactating women (235a); as far
as other mammals are concerned, the writer can find references only to
the lactating cow (235b). It would be interesting to know whether the
unfortunate condition of gynecomastia in men is accompanied by
lactosuria.
2. Other Reducing Oligosaccharides
In this section consideration will be confined to substances other
than lactose and its derivatives, which have been definitely identified in
tissues or products of biological origin. A number of di- and higher
saccharides have been found in small amounts; as has been already
stated these substances are obviously metabolic intermediates in the
hydrolytic fusion of larger molecules or in the anabolic production of
more complicated carbohydrates. Little is known of the existence of
these processes although a few enzymes with transglycosylating activity
have been found, for example, the plant "D -enzyme" of Rees, the bacterial "amylomaltase" of Monod and Torriani, and the rat liver enzyme
of M. R. Stetten (235c).
The remainder of the reducing saccharides to be described in this
section are derived from "typical glycosides." A number of di- and
higher saccharides occur, chiefly in steroid glycosides, in which the
modes of combination of the monosaccharide units are not yet established; these substances are therefore omitted. Di- and higher saccharides obtained synthetically or by controlled hydrolysis of polysaccharides are likewise not described.
Table V summarizes the main bulk of the natural oligosaccharides.