8. POLYSACCHARIDASES
357
The classification of polysaccharidases as to enzymatic specificity
would then be analogous to the classification of polysaccharides according to their chemical composition and structure (see Table I).
In spite of the tremendous number of theoretically possible polysaccharide hydrolyzing enzymes, a relatively small number of such
enzymes has been investigated so far and sufficiently characterized to
warrant their discussion for the purpose of a comparative treatise. A
large number of polysaccharidases has been detected only in lower
plant life; i.e., in bacteria, molds, or yeasts and there, frequently only
in one or two particular organisms.
Enzymes like maltase, cellobiase, and saccharase will not be included in the present discussion since their respective substrates are
disaccharides rather than polysaccharides. Furthermore, enzymes that
catalyze the synthesis as well as the degradation of polysaccharides
through nonhydrolytic transfer reactions do not belong to the class of
hydrolases and will not be discussed, therefore, with the polysaccharidases.
II. The Enzymes of Glycogen and Starch Degradation
Among all polysaccharidases, greatest interest has been attracted
by the enzymes digesting starch and glycogen because of the widespread occurrence of their substrates in nature and because of the obvious and marked effect produced by their action. Thus, as early as
1811, Kirchhoff (2) reported the digestive action of wheat extracts upon
starch, which probably constitutes the first description of an enzymatic
process. Similar phenomena were soon described in other sources,
namely, in saliva by Leuchs (3), in malt by Pay en and Persoz (4), and
in pancreas by Bouchardat (5). The active principle of saliva was
termed ptyalin by Berzelius, and that of malt was called diastase by
Payen and Persoz. Later, it was suggested by Beijerinck (6) to term
all starch-digesting enzymes amylases. Such enzymes have subsequently
been found in a large variety of other sources, notably in blood and
urine, in numerous higher plants, and in a great number of different
microorganisms.
From our present knowledge of the chemical structure of starch
and glycogen and of the mechanism of their enzymatic digestion we
can recognize at least six distinct classes of enzymes causing degradation of these substances.
a. Hydrolytic enzymes which split «-1,4-glucosidic linkages and produce mainly maltose, maltotriose, higher molecular weight oligosaccharides and dextrins, but only insignificant amounts of glucose. These
enzymes are α-amylases and ß-amylases.
357
The classification of polysaccharidases as to enzymatic specificity
would then be analogous to the classification of polysaccharides according to their chemical composition and structure (see Table I).
In spite of the tremendous number of theoretically possible polysaccharide hydrolyzing enzymes, a relatively small number of such
enzymes has been investigated so far and sufficiently characterized to
warrant their discussion for the purpose of a comparative treatise. A
large number of polysaccharidases has been detected only in lower
plant life; i.e., in bacteria, molds, or yeasts and there, frequently only
in one or two particular organisms.
Enzymes like maltase, cellobiase, and saccharase will not be included in the present discussion since their respective substrates are
disaccharides rather than polysaccharides. Furthermore, enzymes that
catalyze the synthesis as well as the degradation of polysaccharides
through nonhydrolytic transfer reactions do not belong to the class of
hydrolases and will not be discussed, therefore, with the polysaccharidases.
II. The Enzymes of Glycogen and Starch Degradation
Among all polysaccharidases, greatest interest has been attracted
by the enzymes digesting starch and glycogen because of the widespread occurrence of their substrates in nature and because of the obvious and marked effect produced by their action. Thus, as early as
1811, Kirchhoff (2) reported the digestive action of wheat extracts upon
starch, which probably constitutes the first description of an enzymatic
process. Similar phenomena were soon described in other sources,
namely, in saliva by Leuchs (3), in malt by Pay en and Persoz (4), and
in pancreas by Bouchardat (5). The active principle of saliva was
termed ptyalin by Berzelius, and that of malt was called diastase by
Payen and Persoz. Later, it was suggested by Beijerinck (6) to term
all starch-digesting enzymes amylases. Such enzymes have subsequently
been found in a large variety of other sources, notably in blood and
urine, in numerous higher plants, and in a great number of different
microorganisms.
From our present knowledge of the chemical structure of starch
and glycogen and of the mechanism of their enzymatic digestion we
can recognize at least six distinct classes of enzymes causing degradation of these substances.
a. Hydrolytic enzymes which split «-1,4-glucosidic linkages and produce mainly maltose, maltotriose, higher molecular weight oligosaccharides and dextrins, but only insignificant amounts of glucose. These
enzymes are α-amylases and ß-amylases.