416
ERNEST BUEDING AND EMMANUEL FÄRBER
inorganic phosphate, but with a decrease in fructose phosphates. These
investigators ascribe the Pasteur effect to an inhibition of phosphofructokinase and perhaps also of hexokinase activity, produced by a
compound formed during oxidative phosphorylation. Whether or not
the activity of these enzymes was inhibited under these conditions was
not determined. The discrepancies in the results obtained with the combined use of soluble glycolytic enzymes and mitochondria may be due
to differences in the experimental conditions, and to variations in the
source and purity of glycolytic enzymes and the ratios between particulate and soluble material. Interpretation of these data is complicated
further by the problem of whether, and to what extent, these experimental conditions approach those prevailing in the intact cell. On the
other hand, the evidence obtained with cell-free preparations are of
great value in pointing out possible mechanisms operating in the intact
cell.
The possibility that the Pasteur effect may be due to a direct inhibitory effect of oxygen on glycolytic enzymes (especially SH-containing enzymes) or of oxidative metabolism has been pointed out by Lippmann (31) and by Engelhardt and Sakov (40).
While the mechanism of the Pasteur effect has not been elucidated
fully, it is evident that its operation insures an efficient utilization of
energy and a conservation of carbohydrate for the cell, because energy
yield from the oxidation of glucose is over ten times greater than from
its conversion to lactic acid.
Although the Pasteur effect has been demonstrated in numerous
cells and tissues, it does not occur in all organisms. For example, utilization of glucose is the same under aerobic and anaerobic conditions in
the parasitic trematodes Schistosoma mansoni (41) and FascioL·
hepatica (42), and in the nematodes Ascaris lumbricoides (43), Parascaris equorum (44), Ascaridia galli (45), and Dracunculus insignis
(46). These helminths take up oxygen when it is available to them, but
they do not depend on respiratory metabolism for survival (47, 48).
Possibly these parasites do not derive or utilize energy from oxidative
metabolism. If this were the case the Pasteur effect, by reducing fermentations, would deprive these organisms from a source of energy. Other
helminths, such as the larvae of Eustrongylides ignotus (49) or
Litomosoides carinii (50), are dependant on respiratory metabolism. In
these two nematodes a Pasteur effect has been demonstrated. Therefore,
the operation of the Pasteur effect in a given organism might indicate
that the latter is able to utilize energy generated from oxidative metabolism.
ERNEST BUEDING AND EMMANUEL FÄRBER
inorganic phosphate, but with a decrease in fructose phosphates. These
investigators ascribe the Pasteur effect to an inhibition of phosphofructokinase and perhaps also of hexokinase activity, produced by a
compound formed during oxidative phosphorylation. Whether or not
the activity of these enzymes was inhibited under these conditions was
not determined. The discrepancies in the results obtained with the combined use of soluble glycolytic enzymes and mitochondria may be due
to differences in the experimental conditions, and to variations in the
source and purity of glycolytic enzymes and the ratios between particulate and soluble material. Interpretation of these data is complicated
further by the problem of whether, and to what extent, these experimental conditions approach those prevailing in the intact cell. On the
other hand, the evidence obtained with cell-free preparations are of
great value in pointing out possible mechanisms operating in the intact
cell.
The possibility that the Pasteur effect may be due to a direct inhibitory effect of oxygen on glycolytic enzymes (especially SH-containing enzymes) or of oxidative metabolism has been pointed out by Lippmann (31) and by Engelhardt and Sakov (40).
While the mechanism of the Pasteur effect has not been elucidated
fully, it is evident that its operation insures an efficient utilization of
energy and a conservation of carbohydrate for the cell, because energy
yield from the oxidation of glucose is over ten times greater than from
its conversion to lactic acid.
Although the Pasteur effect has been demonstrated in numerous
cells and tissues, it does not occur in all organisms. For example, utilization of glucose is the same under aerobic and anaerobic conditions in
the parasitic trematodes Schistosoma mansoni (41) and FascioL·
hepatica (42), and in the nematodes Ascaris lumbricoides (43), Parascaris equorum (44), Ascaridia galli (45), and Dracunculus insignis
(46). These helminths take up oxygen when it is available to them, but
they do not depend on respiratory metabolism for survival (47, 48).
Possibly these parasites do not derive or utilize energy from oxidative
metabolism. If this were the case the Pasteur effect, by reducing fermentations, would deprive these organisms from a source of energy. Other
helminths, such as the larvae of Eustrongylides ignotus (49) or
Litomosoides carinii (50), are dependant on respiratory metabolism. In
these two nematodes a Pasteur effect has been demonstrated. Therefore,
the operation of the Pasteur effect in a given organism might indicate
that the latter is able to utilize energy generated from oxidative metabolism.