418
ERNEST BUEDING AND EMMANUEL FÄRBER
teria, the contribution of each of these pathways varies greatly from
one species to the other. In many organisms such as in lactobacilli (95,
96), clostridia (97-100), staphylococci (84), streptococci (101), and
propionic acid bacteria (102-104) glycolysis is the predominant, but
not necessarily the exclusive pathway of carbohydrate utilization.
There is evidence for a more or less pronounced role of the pentosephosphate pathway in many other microorganisms (79, 86,105-117) and
in certain pseudomonads and aerobacters the pathway via 2-keto-3desoxy-6-phosphogluconate appears to be the major route of carbohydrate utilization (80,118). Some contribution to the latter is made by
the pentose phosphate route (119), but it is doubtful whether the
Embden-Meyerhof scheme operates at all in these organisms (120)
because cell-free extracts of pseudomonads do not ferment* glucose-6phosphate or fructose-l,6-diphosphate, nor do they possess hexokinase or
phosphofructokinase activities (79, 80, 118). Thus, glycolysis is by no
means the exclusive mechanism of carbohydrate utilization in bacteria
and the role and the contribution of the Embden-Meyerhof scheme must
be ascertained in every organism whose metabolism is investigated.
B. PLANTS
The presence in plants of a number of glycolytic enzymes has been
demonstrated (121-124). In the course of these studies an important
difference has been uncovered between one homologous glycolytic enzyme occurring in plants and that of bacteria, yeast, and animals. The
glyceraldehyde-3-phosphate dehydrogenases of,the latter cells and tissues
specifically react with DPN. On the other hand, three types of glyceraldehyde-3-phosphate dehydrogenases have been found in plants. One
of them reacts with DPN, another one with TPN, and a third type,
which is TPN-linked also, catalyzes the oxidation of glyceraldehyde-3phosphate to 3-phosphoglycerate without the participation of phosphate
(or arsenate) and without the intermediate formation of 1,3-diphosphoglycerate (120,125-130). Since TPN-specific glyceraldehyde-3-phosphate
dehydrogenases occur only in plant tissues exposed to light (120, 127,
129), it is possible that the formation of these enzymes has some relationship with photosynthesis.
Plants have been among the first tissues in which the occurrence of
the pentose phosphate pathway of glucose utilization has been demonstrated (127, 130, 131-138) and investigations of plant enzymes have
contributed significantly to an understanding of the reactions involved
* In this chapter the term fermentation is used for anaerobic metabolism of
carbohydrate while the term glycolysis is reserved for the conversion of carbohydrate
to lactic acid, a special case of fermentation.
ERNEST BUEDING AND EMMANUEL FÄRBER
teria, the contribution of each of these pathways varies greatly from
one species to the other. In many organisms such as in lactobacilli (95,
96), clostridia (97-100), staphylococci (84), streptococci (101), and
propionic acid bacteria (102-104) glycolysis is the predominant, but
not necessarily the exclusive pathway of carbohydrate utilization.
There is evidence for a more or less pronounced role of the pentosephosphate pathway in many other microorganisms (79, 86,105-117) and
in certain pseudomonads and aerobacters the pathway via 2-keto-3desoxy-6-phosphogluconate appears to be the major route of carbohydrate utilization (80,118). Some contribution to the latter is made by
the pentose phosphate route (119), but it is doubtful whether the
Embden-Meyerhof scheme operates at all in these organisms (120)
because cell-free extracts of pseudomonads do not ferment* glucose-6phosphate or fructose-l,6-diphosphate, nor do they possess hexokinase or
phosphofructokinase activities (79, 80, 118). Thus, glycolysis is by no
means the exclusive mechanism of carbohydrate utilization in bacteria
and the role and the contribution of the Embden-Meyerhof scheme must
be ascertained in every organism whose metabolism is investigated.
B. PLANTS
The presence in plants of a number of glycolytic enzymes has been
demonstrated (121-124). In the course of these studies an important
difference has been uncovered between one homologous glycolytic enzyme occurring in plants and that of bacteria, yeast, and animals. The
glyceraldehyde-3-phosphate dehydrogenases of,the latter cells and tissues
specifically react with DPN. On the other hand, three types of glyceraldehyde-3-phosphate dehydrogenases have been found in plants. One
of them reacts with DPN, another one with TPN, and a third type,
which is TPN-linked also, catalyzes the oxidation of glyceraldehyde-3phosphate to 3-phosphoglycerate without the participation of phosphate
(or arsenate) and without the intermediate formation of 1,3-diphosphoglycerate (120,125-130). Since TPN-specific glyceraldehyde-3-phosphate
dehydrogenases occur only in plant tissues exposed to light (120, 127,
129), it is possible that the formation of these enzymes has some relationship with photosynthesis.
Plants have been among the first tissues in which the occurrence of
the pentose phosphate pathway of glucose utilization has been demonstrated (127, 130, 131-138) and investigations of plant enzymes have
contributed significantly to an understanding of the reactions involved
* In this chapter the term fermentation is used for anaerobic metabolism of
carbohydrate while the term glycolysis is reserved for the conversion of carbohydrate
to lactic acid, a special case of fermentation.