Hexose Monophosphate Oxidative Pathway Research Articles

Formation of superoxide anions and hydrogen peroxide by polymorphonuclear leukocytes stimulated with cytochalasin.

Cyanide-insensitive respiration of polymorphonuclear leukocytes is induced by the D or E type of cytochalasins, a family of antibiotics which inhibits various cellular motile functions including membrane movement(Nakagawara et al.,1974). The respiratory stimulation is accompanied by the release of superoxide anions and the activated hexose monophosphate oxidative pathway but without any formation of phagosomes(Nakagawara et al.,1976). The cytochalasins D and E are ideal reagents for studying phagocytotic metabolic changes, because they inhibit endocytotic process at the same time. We are going to show the properties of the burst reactions triggered with cytochalasin D or E and compare the reactions with those occur during the ingestion of bacteria.

Anaerobic glucose and serine metabolism in Staphylococcus epidermidis.

Anaerobically grown Staphylococcus epidermidis fermented glucose with the production of lactate and trace amounts of acetate, formate and CO2. Isotopic and inhibitor studies, assays for key enzymes of different metabolic pathways, and fermentation balances, all indicated that glucose was metabolized principally via glycolysis and to a very limited extent by the hexose monophosphate oxidative pathway. Serine fermentation proceeded via deamination and dismutation yielding NH3 and equimolar amounts of lactate, acetate and CO2; small amounts of formate arose by the operation of pyruvate-formate lyase. Incorporation of 0.5% (w/v) glucose in the growth medium depressed serine metabolism by repressing the activities of serine dehydratase and pyruvate dehydrogenase but, conversely, enhanced the activities of phosphofructokinase and lactate dehydrogenase. Glucose-grown organisms at various stages of anaerobic batch growth showed an inverse relationship between the rates of fermentation of serine and glucose. L-Lactate dehydrogenase activity in crude extracts depended on fructose 1,6-bisphosphate, and fructose 1,6-bisphosphate aldolase was found to be a class I aldolase. Despite the presence of ribokinase, D-ribose-5-phosphate isomerase, transaldolase and transketolase, the organisms utilized ribose only after growth aerobically in basal medium, and then at a slow rate after an initial lag period.

Metabolic deactivation of hexavalent chromium mutagenicity

Hexavalent chromium compounds (sodium dichromate, potassium chromate, chromic acid, basic zinc chromate and basic lead chromate) were found to be mutagenic for his − strains of S. typhimurium by inducing both frameshifts and base-pair substitutions. However, addition of either microsomal fractions from rat liver or of human erythrocyte lysates resulted in a complete loss of mutagenicity. As confirmed by chemical analysis, reversal of mutagenicity could be ascribed to reduction of the metal to the inactive trivalent form through a simple oxido-reductive reaction. In fact, reducing agents (ascorbic acid and sodium sulfite) and metabolites (GSH, DPNH and TPNH, either directly tested or obtained by mixing G6PD with S-9 mix) prevented hexavalent chromium mutagenicity, whereas an oxidizing agent (potassium permanganate) totally inhibited reversal of mutagenicity by liver and erythrocyte preparations. Enzymic conversion appeared to be involved in deactivation processes through a large production of TPNH via the hexose monophosphate oxidative pathway and other ancillary systems. On the other hand, microsomal preparations from rat lung displayed an extremely poor inactivating effect on chromium mutagenicity, and those from rat muscle, as well as human serum or plasma, were ineffective. These findings could bear relevance for the elective localization of chromium-induced tumors in human lung and could account for the results of animal carcinogenicity tests, which generally showed the development of tumors, but only at implant sites.

Action of cytochalasin E on polymorphonuclear leucocytes of guinea pig peritoneal exudates

Actions of cytochalasins on polymorphonuclear leucocytes of guinea pig peritoneal exudates have been studied. When the leucocytes were treated with cytochalasin E, complete disappearance of pseudopods was observed during a time, which would be related with the inhibition of particle ingestion. Intracellular granules migrated to the cell periphery in ectoplasma and were afterwards excluded from the cells. Later, formation of cytoplasmic protuberations with irregular shapes and variable diameters (“zeiosis”) and of large vacuoles were observed. Similar changes were also observed in monocytes. These morphological changes were accompanied with metabolic alterations which mimicked those observed during phagocytosis: appearance of cyanide-insensitive respiration, stimulation of hexose monophosphate oxidative pathway and release of superoxide anions and lysosomal enzymes into suspending medium. Other members of the cytochalasin family, cytochalasin C and D, similarly induced release of superoxide anions, whereas cytochalasin A and B had no such effect on leucocytes. Cytochalasin E seemed to have dual effects on leucocytes, namely, (1) inhibition of cytokinesis which is a common effect of the cytochalasin family; and (2) triggering of metabolic changes and degranulation which are characteristics of phagocytotic process.

Metabolic pattern of polymorphonuclear leucocytes induced by trypsin-digested microsomes.

The addition of trypsin [EC 3.4.21.4]-digested liver microsimes induced cyanideinsensitive respiration in guinea pig polymorphonuclear leucocytes with concomitant acceleration of the hexose monophosphate oxidative pathway. The respiration was insensitive to inhibitors of mitochondrial respiration but sensitive to glycolytic inhibitors. These metabolic alterations are similar to those associated with phagocytosis, though the digested mocrosomes were apparently not taken up by the cells and prpbably trigger the netabolic changes by interaction with the cellular membrane. Intact microsomes or microsomes treated with chymotrypsin [EC 3.4.21.1], bacterial proteinase, ribonuclease [EC 3.1.4.22], or neuraminidase [EC 3.2.1.18] could not induce such respiration.

5-Keto-D-fructose: formation and utilization in the course of D-fructose as similation by Gluconabacter cerinus.

The accumulation of 5-keto-d-fructose (5KF) by Gluconobacter cerinus grown on d-fructose in unbuffered medium was shown to be optimal at pH 4.0 after cell growth ceased. During the exponential phase of growth or at neutral pH after the onset of the stationary phase, 5KF production continued but did not accumulate because of its rapid reutilization by reduction to d-fructose. The extent of isotope incorporation into C5 of ribonucleic acid ribose when cells were grown in the presence of specifically labeled d-glucose and d-fructose clearly indicated that (i) the hexose monophosphate oxidative pathway is the predominant metabolic route for carbohydrate assimilation and (ii) extensive randomization of label between C1 and C6 of d-fructose occurred prior to its conversion into pentose. It is suggested that the cyclic oxidation and reduction through the symmetrical 5KF molecule, which accounts for the observed randomization of isotope in d-fructose, provides the cells with an effective mechanism for the regeneration of nicotinamide adenine dinucleotide phosphate during the period of intensive growth.

Effect of low dietary levels of glucose, fructose and sucrose on rat lipid metabolism

The effects of dietary carbohydrates on lipid metabolism have been investigated in rats maintained on diets containing 12 % glucose, fructose or sucrose and appreciable quantities of starch. The changes in hepatic rates of synthesis and catabolism of cholesterol and fatty acids as well as of triglycerides and phospholipids were studied to determine the relative influence of the three sugars on serum lipid concentrations. Marked increase in serum cholesterol results from feeding a sucrose diet, while elevation of serum neutral lipids is obtained with regimens containing fructose and sucrose. The effects are mainly due to the stimulation of rates of lipogenesis, associated with increments in the activities of enzymes of the hexose monophosphate oxidative pathway in the liver, coupled with relative lowering of the catabolic rate of specific lipid classes on respective carbohydrate regimens. Increased rates of triglyceride synthesis in the liver are responsible for elevated serum neutral lipid concentrations in rats on fructose and surcrose diets and are related to the high-α-glycerophosphate dehydrogenase activity in the liver of these animals. Evidence of induced phospho-fructokinase activity by fructose feeding has also been obtained and may be of significance in maintaining a high rate of supply of α-glycerophosphate via dihydroxy-acetone phosphate. Although glucose was found to stimulate hepatic cholesterolo-genesis, it reduced the serum cholesterol level by simultaneously maintaining a high rate of sterol catabolism in the liver. In spite of low sterol degradation rates in the liver of rats fed a fructose regimen, the serum cholesterol level was not significantly altered because hepatic cholesterol synthesis was depressed due to a relative increase in the rate of hepatic fatty acid synthesis from acetate.

PATHWAYS OF GLUCOSE CATABOLISM IN BACILLUS CEREUS.

Goldman, Manuel (The University of Michigan, Ann Arbor), and Harold J. Blumenthal. Pathways of glucose catabolism in Bacillus cereus. J. Bacteriol. 87:377-386. 1964.-Estimates by a radiorespirometric method of the pathways of glucose catabolism of resting-cell suspensions of Bacillus cereus strain terminalis indicate that the Embden-Meyerhof pathway predominates at every stage of development, including the sporogenic and germinative phases. At the filamentous, granular, forespore, and transitional stages, 98% of the glucose was catabolized by the Embden-Meyerhof pathway, and the remainder by the hexose monophosphate oxidative pathway. Estimates of the pathways in resting spore-suspensions arrested at defined stages of development indicate that 20% of the glucose was catabolized through the hexose monophosphate pathway in germinated spores, and 10% in the swollen and elongated stages of postgermination. In cells which had completed the first cell division, the figure fell to about 2%, a level similar to that found for vegetative cells at later stages of development. The key Embden-Meyerhof enzymes, hexokinase, phosphohexoisomerase, phosphofructokinase, and aldolase, as well as several other enzymes, were present at all stages of germination and postgerminative development, supporting the radioisotopic data obtained with whole cells. As indicated by the release of C(14)O(2) from glucose-6-C(14), terminal respiration of resting-cell suspensions operates maximally in vegetative cells at the granular, fore-spore, and transitional stages. There was marked inhibition of terminal respiration during the development of spores into vegetative cells. Only slight activity occurred in the earliest vegetative stages, and maximal operation developed after about ten cell divisions. Fumarase was absent in spores until sometime late in the elongation stage. At this point, a weak but definite activity appeared which increased during later stages of development so that, by the end of about the sixth cell division, fumarase had a specific activity about 80 times that observed at elongation.

The relation of lipogenesis to reduced triphosphopyridine nucleotide generation and to certain enzyme activities in the liver of the “totally” depancreatized rat

1. 1. Evidence that the depressed lipogenesis observed in the liver of the diabetic animal is not the result of decreased TPNH generation via the hexose monophosphate oxidative pathway is provided by experiments carried out with rats 24 h after they were depancreatized by a procedure that ensured removal of more than 99.5% of the pancreas. For three days before pancreatectomy, these rats were fed a diet containing 60% glucose. The presence of diabetes at this early interval after pancreatectomy was indicated by the blood-sugar response, the presence of glucose and ketone bodies in the urine, and by increased amounts of fat in the liver. For controls we used normal rats and rats that had been subjected to laparotomy and manipulation of the abdominal viscera. 2. 2. Fatty acid synthesis from acetate was studied in a system consisting of a supernatant fraction plus microsomes prepared from homogenates of the livers. Lipogenesis from acetate was severely depressed at the 24-h interval after “total” pancreatectomy, but at that time the levels of activities of the two dehydrogenases concerned with glucose 6-phosphate and gluconic acid 6-phosphate were not depressed. 3. 3. Actual measurements of the TPNH produced from glucose 6-phosphate and citrate by the supernatant-microsomal system prepared from the livers of normal, sham-operated and “totally” depancreatized rats were made. TPNH generation by the diabetic system was well within the normal range. 4. 4. The levels of activities of isocitric dehydrogenase and aconitase, enzymes concerned with TPNH production from citrate, were about the same in the livers of normal controls and depancreatized rats. 5. 5. The existence of a powerful system for the reoxidation of TPNH, other than that concerned with fatty acid synthesis, and its effect upon TPN-dependent substrate oxidations are discussed.

Ribose biosynthesis by Streptococcus faecalis

Ribose biosynthesis was studied in Streptococcus faecalis by growing the organism on glucose-1-C 14, -2-C 14, and -6-C 14 and isolating ribose from ribonucleic acid. The labeling pattern of ribose thus obtained suggests that two pathways exist in the formation of ribose. Calculations based on the isotope data suggest that 60% of the ribose is formed by way of the hexose monophosphate oxidative pathway. The other 40% of the ribose has an isotope composition similar to that obtained by the anaerobic reactions of the pentose phosphate pathway. However, failure to detect the enzyme transaldolase makes this possibility unlikely, and an alternative pathway of ribose synthesis using transketolase and aldolase has been suggested.

Role of the Glycolytic Enzyme System in the Germination of Spores of Bacillus coagulans var. thermoacidurans

RECENT work by Halvorson and Church1,2 has shown that the spores of Bacillus cereus var. terminalis contain a functional hexose monophosphate oxidative pathway but no Embden-Meyerhof pathway. Our studies, however, show that the spores of Bacillus coagulans var. thermoacidurans (A.T.C.C. 8038) have a complete glycolytic enzyme system which seems to play an important part in the early stages of germination.

The metabolism of neoplastic tissues: further studies on the hexosemonophosphate oxidative pathway.

The Metabolism of Neoplastic Tissues: Further Studies on the Hexosemonophosphate Oxidative Pathway

OXIDATIVE METABOLISM OF CARBOHYDRATES IN INSECTS: III. HEXOSE MONOPHOSPHATE OXIDATIVE CYCLE IN THE HOUSEFLY, MUSCA DOMESTICA L.

The component reactions of the hexose monophosphate oxidative pathway have been studied in adult houseflies. It has been shown that houseflies possess an active glucose-6-phosphate dehydrogenase, 6-phosphogluconolactonase, 6-phosphogluconic dehydrogenase, phosphopentose isomerase, phosphoketopentose epimerase, transketolase, and transaldolase.The cycle consists of five main steps: (a) a two-step oxidation of glucose-6-phosphate to ribulose-5-phosphate and CO2; (b) isomerization of ribulose-5-phosphate to ribose-5-phosphate; (c) epimerization of ribulose-5-phosphate to xylulose-5-phosphate; (d) conversion of pentose phosphate to sedoheptulose phosphate and triose phosphate; (e) conversion of sedoheptulose phosphate to hexose phosphate.Balance studies indicate that 2 moles of pentose phosphate are utilized for the formation of 1 mole of heptulose phosphate. However, this stoichiometry is attained after a lag period, suggesting the formation of a transient intermediate. Because the lag was eliminated by the addition of hydroxypyruvate, it is suggested that the lag was due to the time required for the combination of a C2fragment with an appropriate aldehyde acceptor.

OXIDATIVE METABOLISM OF CARBOHYDRATES IN INSECTS: III. HEXOSE MONOPHOSPHATE OXIDATIVE CYCLE IN THE HOUSEFLY, MUSCA DOMESTICA L.

The component reactions of the hexose monophosphate oxidative pathway have been studied in adult houseflies. It has been shown that houseflies possess an active glucose-6-phosphate dehydrogenase, 6-phosphogluconolactonase, 6-phosphogluconic dehydrogenase, phosphopentose isomerase, phosphoketopentose epimerase, transketolase, and transaldolase.The cycle consists of five main steps: (a) a two-step oxidation of glucose-6-phosphate to ribulose-5-phosphate and CO2; (b) isomerization of ribulose-5-phosphate to ribose-5-phosphate; (c) epimerization of ribulose-5-phosphate to xylulose-5-phosphate; (d) conversion of pentose phosphate to sedoheptulose phosphate and triose phosphate; (e) conversion of sedoheptulose phosphate to hexose phosphate.Balance studies indicate that 2 moles of pentose phosphate are utilized for the formation of 1 mole of heptulose phosphate. However, this stoichiometry is attained after a lag period, suggesting the formation of a transient intermediate. Because the lag was eliminated by the addition of hydroxypyruvate, it is suggested that the lag was due to the time required for the combination of a C2fragment with an appropriate aldehyde acceptor.

The metabolism of neoplastic tissues: demonstration of intermediates and reaction sequences of the hexose monophosphate oxidative pathway.

The Metabolism of Neoplastic Tissues: Demonstration of Intermediates and Reaction Sequences of the Hexose Monophosphate Oxidative Pathway

A preliminary investigation of the hormonal control of the hexose monophosphate oxidative pathway.

A preliminary investigation of the hormonal control of the hexose monophosphate oxidative pathway.