8. POLYSACCHARIDASES
407
malian α-amylases, in particular with regard to pH optima and NaCl
activation.
5. Conclusions
The biological degradation of pectic substances is achieved by at
least two different enzymes, possibly by a larger number; i.e., one that
solubilizes the insoluble protopectin (protopectinase), a second that depolymerizes the substrate (depolymerase), a third (pectin esterase) that
splits off methyl ester groups, and a fourth (polygalacturonase) that
breaks down the remainder of the substrate to galacturonic acid.
Whether protopectinase, depolymerase, and polygalacturonase are actually different enzymes cannot be ascertained on the basis of the information available. It appears that in many instances the enzymes
occur together; they are found rarely in animals, frequently, however,
in higher plants and in molds. At least one of the pectic enzymes (pectin
esterase) has been reported to be of different nature whether it occurs
in molds or in higher plants.
If it is true that protopectinase, depolymerase, and polygalacturonase
are different enzymes, certain analogies of the pectic enzymes with the
amylolytic enzymes become evident. Protopectinase, depolymerase, and
polygalacturonase supposedly split the same type of glycosidic linkage
in their substrate, and so do α-amylases, ß-amylases, and a-l,4-glucosidases in starch. A second type of a chemical bond in the pectic substances (methyl ester groups) is hydrolyzed by a different enzyme (pectin esterase) and, in analogy to this, a second type of bond in amylopectin (a-l,6-glucosidic linkage) is hydrolyzed by an enzyme specific
only for this bond (amylo-l,6-glucosidase).
There is no doubt that pectic enzymes together with cellulases play a
major role in the solubilization of insoluble cell wall material of plant
life. It is understandable, therefore, that these enzymes occur mostly in
plants, in microorganisms, and, in isolated cases (cellulases), in the
digestive tract of some animals, mainly herbivores.
Pectic enzymes were found not to play a major role in the wilting of
plants invaded by certain bacteria (303). This process is obviously due
to cellulytic enzymes alone.
B. ALGINASE
Alginic acid is a seaweed polysaccharide made up entirely of Dmannuronic acid units linked together to unbranched chains by ß-1,4bonds.
Alginase activity, as measured by the reduction of the viscosity of
alginic acid solutions, has been reported in bacteria, where its occur-
407
malian α-amylases, in particular with regard to pH optima and NaCl
activation.
5. Conclusions
The biological degradation of pectic substances is achieved by at
least two different enzymes, possibly by a larger number; i.e., one that
solubilizes the insoluble protopectin (protopectinase), a second that depolymerizes the substrate (depolymerase), a third (pectin esterase) that
splits off methyl ester groups, and a fourth (polygalacturonase) that
breaks down the remainder of the substrate to galacturonic acid.
Whether protopectinase, depolymerase, and polygalacturonase are actually different enzymes cannot be ascertained on the basis of the information available. It appears that in many instances the enzymes
occur together; they are found rarely in animals, frequently, however,
in higher plants and in molds. At least one of the pectic enzymes (pectin
esterase) has been reported to be of different nature whether it occurs
in molds or in higher plants.
If it is true that protopectinase, depolymerase, and polygalacturonase
are different enzymes, certain analogies of the pectic enzymes with the
amylolytic enzymes become evident. Protopectinase, depolymerase, and
polygalacturonase supposedly split the same type of glycosidic linkage
in their substrate, and so do α-amylases, ß-amylases, and a-l,4-glucosidases in starch. A second type of a chemical bond in the pectic substances (methyl ester groups) is hydrolyzed by a different enzyme (pectin esterase) and, in analogy to this, a second type of bond in amylopectin (a-l,6-glucosidic linkage) is hydrolyzed by an enzyme specific
only for this bond (amylo-l,6-glucosidase).
There is no doubt that pectic enzymes together with cellulases play a
major role in the solubilization of insoluble cell wall material of plant
life. It is understandable, therefore, that these enzymes occur mostly in
plants, in microorganisms, and, in isolated cases (cellulases), in the
digestive tract of some animals, mainly herbivores.
Pectic enzymes were found not to play a major role in the wilting of
plants invaded by certain bacteria (303). This process is obviously due
to cellulytic enzymes alone.
B. ALGINASE
Alginic acid is a seaweed polysaccharide made up entirely of Dmannuronic acid units linked together to unbranched chains by ß-1,4bonds.
Alginase activity, as measured by the reduction of the viscosity of
alginic acid solutions, has been reported in bacteria, where its occur-