8. POLYSACCHARIDASES
409
(315, 316) consists apparently in the hydrolysis of the capsular polysaccharide material, with the effect that the decapsulated bacteria become
exposed to the action of phagocytes.
XI. Mucopolysaccharases
In accordance with the generally accepted nomenclature whereby
all those polysaccharides that contain aminosugars are called mucopolysaccharides, the enzymes that hydrolyze this group of natural polymers
are termed mucopolysaccharases. According to the chemical nature of
their substrates, they are to be subdivided into three classes: (a)
enzymes that hydrolyze mucopolysaccharides not containing uronic acid
(chitinase, lysozyme); (b) enzymes that hydrolyze mucopolysaccharides
containing uronic acids, but no sulfate (hyaluronidase); (c) enzymes
that hydrolyze mucopolysaccharides containing sulfate (chondroitin
sulfatase, heparinase).
A. CHITINASE
This enzyme, although classified with the mucopolysaccharases because of the chemical nature of its substrate, has many common traits
with cellulases and other enzymes that hydrolyze insoluble structural
polysaccharides from the cell wall, in particular its occurrence in association with those enzymes.
Karrer and Hof mann (317) described chitinase in the digestive tract
of the Roman snail (Helix pomatia). The product of reaction is Nacetylglucosamine. Fractionation of the enzymes from the snail and from
almonds (emulsin) yielded a chitinase which did not split chitobiose,
i.e., which produced low molecular chitodextrins rather than N-acetylglucosamine as end products (318-321). These authors also found the
presence of a chitobiase in the crude enzyme solutions that they were
able to separate from the chitinase by chromatography.
The importance of the IV-acetyl groups of the substrate on the enzymatic degradation was pointed out by Karrer (253). When partially
deacetylated chitosan served as substrate for the enzyme, the end
products of the reaction were tri- and tetrasaccharides. Only after
acetylation of their amino groups were these dextrins again available
for enzymatic attack.
Besides the occurrence of chitinase in the snail and in plants (emulsin), this enzyme has also been found in molds (322), bacteria, and
actinomyces (295). Chitinase, as well as chitobiase, is secreted by the
epidermis of arthropods (322a,b), by the intestinal walls of earthworms
(322c,d), and by the hepatopancreas of crabs (322e). This enzyme has
been purified from Streptomyces cultures (322f).
409
(315, 316) consists apparently in the hydrolysis of the capsular polysaccharide material, with the effect that the decapsulated bacteria become
exposed to the action of phagocytes.
XI. Mucopolysaccharases
In accordance with the generally accepted nomenclature whereby
all those polysaccharides that contain aminosugars are called mucopolysaccharides, the enzymes that hydrolyze this group of natural polymers
are termed mucopolysaccharases. According to the chemical nature of
their substrates, they are to be subdivided into three classes: (a)
enzymes that hydrolyze mucopolysaccharides not containing uronic acid
(chitinase, lysozyme); (b) enzymes that hydrolyze mucopolysaccharides
containing uronic acids, but no sulfate (hyaluronidase); (c) enzymes
that hydrolyze mucopolysaccharides containing sulfate (chondroitin
sulfatase, heparinase).
A. CHITINASE
This enzyme, although classified with the mucopolysaccharases because of the chemical nature of its substrate, has many common traits
with cellulases and other enzymes that hydrolyze insoluble structural
polysaccharides from the cell wall, in particular its occurrence in association with those enzymes.
Karrer and Hof mann (317) described chitinase in the digestive tract
of the Roman snail (Helix pomatia). The product of reaction is Nacetylglucosamine. Fractionation of the enzymes from the snail and from
almonds (emulsin) yielded a chitinase which did not split chitobiose,
i.e., which produced low molecular chitodextrins rather than N-acetylglucosamine as end products (318-321). These authors also found the
presence of a chitobiase in the crude enzyme solutions that they were
able to separate from the chitinase by chromatography.
The importance of the IV-acetyl groups of the substrate on the enzymatic degradation was pointed out by Karrer (253). When partially
deacetylated chitosan served as substrate for the enzyme, the end
products of the reaction were tri- and tetrasaccharides. Only after
acetylation of their amino groups were these dextrins again available
for enzymatic attack.
Besides the occurrence of chitinase in the snail and in plants (emulsin), this enzyme has also been found in molds (322), bacteria, and
actinomyces (295). Chitinase, as well as chitobiase, is secreted by the
epidermis of arthropods (322a,b), by the intestinal walls of earthworms
(322c,d), and by the hepatopancreas of crabs (322e). This enzyme has
been purified from Streptomyces cultures (322f).