8. POLYSACCHARIDASES
401
V. Enzymes That Hydrolyze Other Polyglucosans
A. LlCHENASE
Lichenin is the polysaccharide of lichens and is similar in structure
to cellulose. It is distinct from the latter, however, by the presence in it
of about 25% of ß-l,3-glucosidic linkages, probably distributed at random
throughout the molecule.
Whether the biological degradation of lichenin is actually due to enzymes different from cellulase, and whether cellulase is able to attack
lichenin, is not exactly known. It is obvious, however, that the action
and, in particular, the occurrence of lichenase are similar to those of
cellulase. Pigman (254), in reviewing this enzyme, indicates its presence in mammals (rabbit pancreas, cattle, and swine stomachs), in
invertebrates (Helix pomatia, sponge, earthworm, starfish, mussel, crab,
etc.), in higher plants (sprouted and dormant barley, wheat, rye, and
oats and also corn, spinach, bean seeds, and hyacinth bulbs), in bacteria (Cytophaga), and in molds. Its abundance in the seeds of most
plants has suggested that its substrate lichenin is more widely distributed in nature than commonly thought (285).
B. LAMINARASE
Laminarin is a polysaccharide of seaweeds composed entirely of Dglucose and is probably built up by ß-l,3-glucosidic bonds. Its biological
degradation by laminarase has been found to yield D-glucose, laminarobiose, and higher oligosaccharides (286). The enzyme has been
found to occur in wheat, oat, barley, potato, and hyacinth bulbs. Its
specificity does not appear to be limited to laminarin since it is also
capable of splitting lichenin. No experiments with purified enzyme
preparations have been published, and it cannot be decided whether
laminarase is different from lichenase and/or cellulase.
VI. Enzymes That Hydrolyze Mannans and Mannogalactans
Because of the fact that the substrates for these enzymes have not
been prepared in sufficiently purified form, only little information is
available on the enzymes. The sources for these enzymes are again
similar to those of cellulose (254), i.e., the gastric juice of the snail
and other mollusks, plant seeds, malt extract, bacteria, and molds
(.Aspergillus oryzae). The possibility that mannan- and mannogalactansplitting enzymes are identical with cellulase must be taken into consideration.
401
V. Enzymes That Hydrolyze Other Polyglucosans
A. LlCHENASE
Lichenin is the polysaccharide of lichens and is similar in structure
to cellulose. It is distinct from the latter, however, by the presence in it
of about 25% of ß-l,3-glucosidic linkages, probably distributed at random
throughout the molecule.
Whether the biological degradation of lichenin is actually due to enzymes different from cellulase, and whether cellulase is able to attack
lichenin, is not exactly known. It is obvious, however, that the action
and, in particular, the occurrence of lichenase are similar to those of
cellulase. Pigman (254), in reviewing this enzyme, indicates its presence in mammals (rabbit pancreas, cattle, and swine stomachs), in
invertebrates (Helix pomatia, sponge, earthworm, starfish, mussel, crab,
etc.), in higher plants (sprouted and dormant barley, wheat, rye, and
oats and also corn, spinach, bean seeds, and hyacinth bulbs), in bacteria (Cytophaga), and in molds. Its abundance in the seeds of most
plants has suggested that its substrate lichenin is more widely distributed in nature than commonly thought (285).
B. LAMINARASE
Laminarin is a polysaccharide of seaweeds composed entirely of Dglucose and is probably built up by ß-l,3-glucosidic bonds. Its biological
degradation by laminarase has been found to yield D-glucose, laminarobiose, and higher oligosaccharides (286). The enzyme has been
found to occur in wheat, oat, barley, potato, and hyacinth bulbs. Its
specificity does not appear to be limited to laminarin since it is also
capable of splitting lichenin. No experiments with purified enzyme
preparations have been published, and it cannot be decided whether
laminarase is different from lichenase and/or cellulase.
VI. Enzymes That Hydrolyze Mannans and Mannogalactans
Because of the fact that the substrates for these enzymes have not
been prepared in sufficiently purified form, only little information is
available on the enzymes. The sources for these enzymes are again
similar to those of cellulose (254), i.e., the gastric juice of the snail
and other mollusks, plant seeds, malt extract, bacteria, and molds
(.Aspergillus oryzae). The possibility that mannan- and mannogalactansplitting enzymes are identical with cellulase must be taken into consideration.