414
PETER BERNFELD
the large group of enzymes capable of destroying the extremely insoluble
structural materials from the cell walls of plant tissue, i.e., cellulases,
lichenase, mannase, xylanase, hemicellulases, the pectic enzymes, etc.
Most polysaccharidases acting on soluble substrates are also of
extracellular nature; they are secreted by various glands of the animal
organism, such as α-amylase from the salivary glands and from the
pancreas, or they are emitted into the culture media by bacteria and
molds, like amylase from Bacillus subtilis and Aspergillus oryzae and
like dextranase from B. cellvibrio and from various Penicillium strains.
Another group of extracellular polysaccharidases are the enzymes
capable of dissolving the more or less gelatinous mucopolysaccharides
surrounding the mammalian ovum and certain bacteria, e.g., hyaluronidase from the semen and from bacteria, and lysozyme.
Only a few polysaccharidases are known to be intracellular enzymes,
such as the α-amylase occurring in rather low concentrations in various
mammalian tissues. Their role is not quite clear, however, and it may
well be that they fulfill an entirely different function from that of the
extracellular pancreatic and salivary amylases. The possibility that
liver amylase may be involved indirectly in the synthesis of glycogen
by maintaining at a constant level the concentration of low molecular
polysaccharidases. The enzymes acting on insoluble substrates form a
action, has been discussed earlier in this chapter.
As it was pointed out before, there is a close relationship between
the extracellular nature of these enzymes and their biological function.
Many of the completely insoluble structural polysaccharides of plant
cell walls, such as cellulose, lichenin, mannan, galactomannan, xylan,
hemicellulose, some pectic substances and, in addition, chitin. may be
made available as a source of energy to organisms excreting specific
polysaccharide or oligosaccharide primers, necessary for phosphorylase
distinct group not only because they have the ability in common to
solubilize their substrates, but also because they closely resemble one
another with respect to their distribution in nature. Thus, they are
found in very similar places; i.e., bacteria and molds and, in a few
instances, in higher plants (barley, potato sprouts), in protozoa
(amebas), and in the intestinal tracts of mollusks and insects. Their occurrence in the animal sources, especially in insects, in clams and some
other mollusks is due, at least in part, to the intestinal flora and fauna
of the animals, rather than to animal origin itself. One comes to the
conclusion, therefore, that the digestion of structural plant cell wall
polysaccharides and of chitin is mostly, if not entirely, carried out by
bacteria, molds, and protozoa, and that lower animals utilizing insoluble
PETER BERNFELD
the large group of enzymes capable of destroying the extremely insoluble
structural materials from the cell walls of plant tissue, i.e., cellulases,
lichenase, mannase, xylanase, hemicellulases, the pectic enzymes, etc.
Most polysaccharidases acting on soluble substrates are also of
extracellular nature; they are secreted by various glands of the animal
organism, such as α-amylase from the salivary glands and from the
pancreas, or they are emitted into the culture media by bacteria and
molds, like amylase from Bacillus subtilis and Aspergillus oryzae and
like dextranase from B. cellvibrio and from various Penicillium strains.
Another group of extracellular polysaccharidases are the enzymes
capable of dissolving the more or less gelatinous mucopolysaccharides
surrounding the mammalian ovum and certain bacteria, e.g., hyaluronidase from the semen and from bacteria, and lysozyme.
Only a few polysaccharidases are known to be intracellular enzymes,
such as the α-amylase occurring in rather low concentrations in various
mammalian tissues. Their role is not quite clear, however, and it may
well be that they fulfill an entirely different function from that of the
extracellular pancreatic and salivary amylases. The possibility that
liver amylase may be involved indirectly in the synthesis of glycogen
by maintaining at a constant level the concentration of low molecular
polysaccharidases. The enzymes acting on insoluble substrates form a
action, has been discussed earlier in this chapter.
As it was pointed out before, there is a close relationship between
the extracellular nature of these enzymes and their biological function.
Many of the completely insoluble structural polysaccharides of plant
cell walls, such as cellulose, lichenin, mannan, galactomannan, xylan,
hemicellulose, some pectic substances and, in addition, chitin. may be
made available as a source of energy to organisms excreting specific
polysaccharide or oligosaccharide primers, necessary for phosphorylase
distinct group not only because they have the ability in common to
solubilize their substrates, but also because they closely resemble one
another with respect to their distribution in nature. Thus, they are
found in very similar places; i.e., bacteria and molds and, in a few
instances, in higher plants (barley, potato sprouts), in protozoa
(amebas), and in the intestinal tracts of mollusks and insects. Their occurrence in the animal sources, especially in insects, in clams and some
other mollusks is due, at least in part, to the intestinal flora and fauna
of the animals, rather than to animal origin itself. One comes to the
conclusion, therefore, that the digestion of structural plant cell wall
polysaccharides and of chitin is mostly, if not entirely, carried out by
bacteria, molds, and protozoa, and that lower animals utilizing insoluble