1. PENTOSE PHOSPHATE CYCLE
63
lished. The level of G-6-P DH did not change significantly during fertilization in the eggs of Arbacia. On the other hand, the activity of this
enzyme increases rapidly immediately after fertilization of the eggs of
Paracentrotus (slightly later in Psammechinus). Ultimately, two separate peaks of G-6-P DH activity are obtained, one at the late cleavage
step and the other at hatching. Subsequently, a gradual decrease of the
dehydrogenase activity takes place.
XI. Roundworms
In general, these worms are particularly rich in both G-6-P DH and
6-PG DH (402). Both enzymes are TPN specific, and in all the cases
tested the activity of 6-PG DH was always less than that of G-6-P DH.
The list of worms possessing one or both of these dehydrogenases is already fairly extensive. A partial list of such organisms is as follows:
Ascaris lumbricoides, Parascaris equorum, Toxacara cams, Ascaridia galli,
Ascaridia columbae, Heterakis gallinae, and Strongylus edentatus
(402).
Other researchers found G-6-P DH activity in homogenates of TrichineUa
spiralis larvae (408), and both G-6-P DH and 6-PG DH in extracts of
Ditylenchus triformis and D. dipsaci (409). In addition, de Ley and
Vercruysse (402) have shown that the extract of the female genital tract
of Ascaris lumbricoides, in the presence of the proper substrates and
TPN
+ regenerating system, forms sedoheptulose. Furthermore, ribose-5phosphate isomerase, xylulose-5-phosphate isomerase (phosphoketopentose epimerase), transketolase (410), and transaldolase (411) were
shown to be present in extracts of the muscles of this parasite. In spite
of all these evidences, however, isotope studies indicate that the major
pathway of glucose catabolism is via glycolysis (411).
XII. Flatworms
In this category, the activity of either G-6-P DH or 6-PG DH ranges
from a very high value for the parasitic cestode Anoplocephala perfoliata, to intermediate values for the free-living planarian Polycelis nigra
and the liver fluke Fasciola hepatica, to zero for the hydatid cyst of
Echinococcus granulosus (402). Other platyhelminths containing these
dehydrogenases, in varying degrees, are the planarian Euplanaria torva;
the trematode Dicrocoelium dendriticum; and the cestodes Moniezia
benedeni, Taenia saginata, Taenia pisiformis, and Dipylidium caninum
(402). The findings that both G-6-P DH and 6-PG DH are lacking in
the larval stage of Echinococcus of the horse liver is in contrast with the
results that both these dehydrogenases do exist in the scolices of sheep
liver hydatid cyst (412). In fact, almost all the enzymes of the pentose
63
lished. The level of G-6-P DH did not change significantly during fertilization in the eggs of Arbacia. On the other hand, the activity of this
enzyme increases rapidly immediately after fertilization of the eggs of
Paracentrotus (slightly later in Psammechinus). Ultimately, two separate peaks of G-6-P DH activity are obtained, one at the late cleavage
step and the other at hatching. Subsequently, a gradual decrease of the
dehydrogenase activity takes place.
XI. Roundworms
In general, these worms are particularly rich in both G-6-P DH and
6-PG DH (402). Both enzymes are TPN specific, and in all the cases
tested the activity of 6-PG DH was always less than that of G-6-P DH.
The list of worms possessing one or both of these dehydrogenases is already fairly extensive. A partial list of such organisms is as follows:
Ascaris lumbricoides, Parascaris equorum, Toxacara cams, Ascaridia galli,
Ascaridia columbae, Heterakis gallinae, and Strongylus edentatus
(402).
Other researchers found G-6-P DH activity in homogenates of TrichineUa
spiralis larvae (408), and both G-6-P DH and 6-PG DH in extracts of
Ditylenchus triformis and D. dipsaci (409). In addition, de Ley and
Vercruysse (402) have shown that the extract of the female genital tract
of Ascaris lumbricoides, in the presence of the proper substrates and
TPN
+ regenerating system, forms sedoheptulose. Furthermore, ribose-5phosphate isomerase, xylulose-5-phosphate isomerase (phosphoketopentose epimerase), transketolase (410), and transaldolase (411) were
shown to be present in extracts of the muscles of this parasite. In spite
of all these evidences, however, isotope studies indicate that the major
pathway of glucose catabolism is via glycolysis (411).
XII. Flatworms
In this category, the activity of either G-6-P DH or 6-PG DH ranges
from a very high value for the parasitic cestode Anoplocephala perfoliata, to intermediate values for the free-living planarian Polycelis nigra
and the liver fluke Fasciola hepatica, to zero for the hydatid cyst of
Echinococcus granulosus (402). Other platyhelminths containing these
dehydrogenases, in varying degrees, are the planarian Euplanaria torva;
the trematode Dicrocoelium dendriticum; and the cestodes Moniezia
benedeni, Taenia saginata, Taenia pisiformis, and Dipylidium caninum
(402). The findings that both G-6-P DH and 6-PG DH are lacking in
the larval stage of Echinococcus of the horse liver is in contrast with the
results that both these dehydrogenases do exist in the scolices of sheep
liver hydatid cyst (412). In fact, almost all the enzymes of the pentose