402
PETER BERNFELD
VII. Enzymes That Hydrolyze Fructans
A. INVERTASE
It has been reported that commercial invertase is capable of hydrolyzing, although rather slowly, so-called glucofructans. Thus, glucofructans from Asphodelus, from daffodils, from Lycoris (287), as well as
two polysaccharides from Allium (288), when incubated with invertase
preparations, undergo a change in their optical rotation which, though
negative in the beginning, turns even more negative during enzymatic
hydrolysis. The mutarotation of the digests is downward in the beginning and becomes upward toward the end of the reaction. The authors
conclude that the downward mutarotation is due to the liberation of
fructose whereas the upward mutarotation is the result of the liberation
of «-glucose.
Fructans containing only fructose are also digested by invertase, and
the fructan phlean isolated from timothy roots (287) as well as a
fructan from Allium ursinum (288) behave in a similar fashion upon
incubation with invertase, with the exception that the mutarotation is
always upward because of the lack of liberation of «-glucose.
B. INULASE
Pringsheim et al. (289, 290) have isolated an enzyme from Aspergillus niger that is capable of hydrolyzing inulin to about 90%. They
later found small amounts of glucose in the digests which contained
mainly fructose (291, 292). Purified inulase preparations from two
samples of bakers' yeast and, to a lesser degree, from three samples of
brewers' yeast were obtained by Adams et al. (293). These authors
noted the appearance of about 1.7% glucose during the hydrolysis which
they ascribed to originate from inulin. The inulase preparations were not
able to hydrolyze a- or ß-dextrins, but contained small amounts of enzymes splitting low molecular weight /?-glycosides.
VIM. Enzymes That Hydrolyze Pentosans (Xylanase)
Xylan together with other polysaccharides, such as mannogalactans
and the so-called hemicelluloses, constitutes a group of plant polysaccharides which have been only incompletely separated from one another. Xylan is the best-defined substance of this group, and its biological
degradation has been the subject of several publications. Again, the
occurrence of xylanase is very similar to that of cellulase and has been
reviewed by Pigman (254). This enzyme is found in mollusks (snails),
insect larvae, higher plants (barley malt), and molds (Aspergillus
PETER BERNFELD
VII. Enzymes That Hydrolyze Fructans
A. INVERTASE
It has been reported that commercial invertase is capable of hydrolyzing, although rather slowly, so-called glucofructans. Thus, glucofructans from Asphodelus, from daffodils, from Lycoris (287), as well as
two polysaccharides from Allium (288), when incubated with invertase
preparations, undergo a change in their optical rotation which, though
negative in the beginning, turns even more negative during enzymatic
hydrolysis. The mutarotation of the digests is downward in the beginning and becomes upward toward the end of the reaction. The authors
conclude that the downward mutarotation is due to the liberation of
fructose whereas the upward mutarotation is the result of the liberation
of «-glucose.
Fructans containing only fructose are also digested by invertase, and
the fructan phlean isolated from timothy roots (287) as well as a
fructan from Allium ursinum (288) behave in a similar fashion upon
incubation with invertase, with the exception that the mutarotation is
always upward because of the lack of liberation of «-glucose.
B. INULASE
Pringsheim et al. (289, 290) have isolated an enzyme from Aspergillus niger that is capable of hydrolyzing inulin to about 90%. They
later found small amounts of glucose in the digests which contained
mainly fructose (291, 292). Purified inulase preparations from two
samples of bakers' yeast and, to a lesser degree, from three samples of
brewers' yeast were obtained by Adams et al. (293). These authors
noted the appearance of about 1.7% glucose during the hydrolysis which
they ascribed to originate from inulin. The inulase preparations were not
able to hydrolyze a- or ß-dextrins, but contained small amounts of enzymes splitting low molecular weight /?-glycosides.
VIM. Enzymes That Hydrolyze Pentosans (Xylanase)
Xylan together with other polysaccharides, such as mannogalactans
and the so-called hemicelluloses, constitutes a group of plant polysaccharides which have been only incompletely separated from one another. Xylan is the best-defined substance of this group, and its biological
degradation has been the subject of several publications. Again, the
occurrence of xylanase is very similar to that of cellulase and has been
reviewed by Pigman (254). This enzyme is found in mollusks (snails),
insect larvae, higher plants (barley malt), and molds (Aspergillus