Glycolytic Sequence Research Articles

Carbohydrate metabolism in Brugia pahangi (Nematoda: Filarioidea)

Carbohydrate metabolism in Brugia pahangi (Nematoda:Filarioidea). International Journal for Parasitology 16: 465–469. Adult B. pahangi have a complete glycolytic sequence and tricarboxylic acid cycle. The activities of the glycolytic enzymes are extremely high, but their relative activities are similar to those found in other glycolytic tissues. A comparison of the mass action ratios of the glycolytic enzymes with their apparent equilibrium constants indicates that phosphorylase, hexokinase, phosphofructokinase and pyruvate kinase are non-equilibrium regulatory enzymes. There is also some evidence that aldolase may be pseudoregulatory. Adult B. pahangi have measurable amounts of fumarate reductase as well as phosphoenolpyruvate carboxykinase and NADP-linked malic enzyme. Apart from lactate. the only other acidic end-product detected was traces of alanine; lactate production was little affected by the presence or absence of oxygen, unless exogenous glucose was present.

Balanced contribution of glycolytic and adenylate pool in supply of metabolic energy in platelets.

When platelets are treated with H2O2 the metabolic ATP content decreases sharply (Holmsen, H., and Robkin, L. (1977) J. Biol. Chem. 252, 1752-1757). Here we report that the loss of metabolic energy is fully recovered in phosphorylated glycolytic intermediates. A mixture of antimycin A/2-deoxy-D-glucose/D-gluconic acid-1,5-lactone blocks mitochondrial ATP resynthesis and prevents the entry of sugars into the glycolytic sequence. The energy-rich phosphates in the adenylate and the glycolytic pool are then consumed in a specific order. First, the glycolytic pool is consumed at a rate of 4.5 mumol of ATP equivalents/min/10(11) cells, and metabolic ATP and ADP are kept stable; then the consumption of the glycolytic pool decreases and metabolic ATP and ADP are consumed, together keeping up with the same rate of energy consumption. Thrombin stimulation increases the energy consumption to about 17 mumol of ATPeq/min/10(11) cells which is now furnished by both the glycolytic and the adenylate pool, again with a preferential consumption of the former. The results show that H2O2 triggers a shift of energy-rich phosphates from the adenylate to the glycolytic pool and that the latter remains rapidly accessible to energy consumption thereby stabilizing the level of metabolic ATP. The adenylate energy charge is independent of the distribution of energy among the two pools, which extends its importance to the regulation of energy supply and demand beyond the adenylate pool.

On the developmental properties and tissue interactions of hexokinase

The interactions of the isozymes of hexokinase with cellular structure have been studied in the major tissues of the mouse during development. Overall, these data provide a clear indication that interactions between hexokinase and cellular structure are appreciable in all major tissues and at all stages of development, and an analysis of the isozyme status of the enzyme in both soluble and bound compartments has been effected. Further evidence in support of the already well documented interaction of hexokinase I to subcellular material in adult brain and kidney tissues is provided and extended to show that such interactions are extensive in both these tissues throughout development. In addition, evidence is provided that considerable hexokinase II activity is present in mouse foetal tissues in both the soluble and bound fractions and this isozyme is also shown to be the predominant "bound" form of the enzyme in adult skeletal muscle. By contrast, hexokinase III and IV are shown to be largely located in the cytosolic fraction of liver. The metabolic implications of these enzyme-structural interactions during development are discussed, as is the possibility of a functional linkage between hexokinase, which is bound to the mitochondria, and other enzymic components of the glycolytic sequence.

Thermoplasma acidophilum: Glucose Degradative Pathways and Respiratory Activities

Soluble extracts of Thermoplasma acidophilum consumed O 2 when provided with anyof a variety of metabolic substrates. About 80 of the total cellular respiratory activity was in the soluble fraction, and about 20 in the particulate membrane fraction. Intermediates in the pentose phosphate pathway and Krebs Cycle were among the best substrates for respiration in vitro . Intermediates in the Embden-Meyerhoff glycolytic sequence were also effective, as were several 1- and 2-carbon compounds such as acetaldehyde and formate. When radioactive 14 C -glucose was given to living cultures the excretory products CO 2 and acetic acid became radioactive. The molar ratio of CO 2 to acetic acid was variable, but generally about 3. Intracellular metabolites that became 14 C-labeled were those expected from the pentose phosphate pathway, glycolysis, and the Krebs Cycle. The disaccharide maltose also became labeled. Although T. acidophilum should have the potential for anaerobic metabolism,experimentally it survived for only about 20 min without O 2 . Continuous aeration is apparently required for the regulation of intracellular pH.

Major volatile metabolites produced by two isolates of Aphelenchus avenae under aerobic and anaerobic conditions

1. 1. Greater quantities of glycerol were detected in aerobic incubates of A. avenae isolate M than in isolate F. No ethanol was detected in aerobic incubates of either isolate. 2. 2. In anaerobic incubates both isolates produced ethanol. 3. 3. 10–20 times more glycerol was detected in anaerobic incubates as opposed to aerobic incubates of both isolates M and F. 4. 4. Isolate M produced more glycerol ( ca. ten-fold) than isolate F under identical conditions. 5. 5. The possible interplay between the A. avenae α-glycerophosphate-oxidase complex and the glycolytic sequence in glycerol production, and the survival value of the latter to this soil dwelling nematode is discussed.

Effects of pregnancy and lactation on the activities in sheep liver of some enzymes of glucose metabolism

SUMMARYThe activities of some enzymes that regulate the gluconeogenic-glycolytic pathway were measured in sheep liver during late pregnancy, at three stages of lactation and after the lambs were weaned. Of the gluconeogenic enzymes, glucose-6-phosphatase and phosphoenolpyruvate carboxylase activities were unchanged throughout pregnancy and lactation and were similar to the values for non-breeding ewes. The activity of fructose diphosphatase increased 2 times and that of pyruvate carboxylase increased 5–7 times during late pregnancy and in early lactation.In the glycolytic sequence phosphofructokinase activity declined by about 50% during lactation. Pyruvate kinase activity declined by about 40% at the end of pregnancy but throughout lactation it was similar to the value for non-breeding ewes. Hexokinase activity was very low in all animals.

The Biochemical Pathway in Triterpene Synthesis in Laticifers ofHoyaandEuphorbia

SummarySuccessful 14C—incorporation into latex triterpenes of Hoya diversifolia and Euphorbia lathyris was obtained by incubating latex bearing plant parts with 14C sugars. Incorporation experiments with specifically labeled glucose revealed a glycolytic sequence of glucose catabolism inside e laticifer prior to isoprene synthesis. The participation of an oxidative pentose cycle was of minor importance. The biochemical aspects and consequences of this direct link between carbohydrate metabolism and lipid synthesis inside a laticifer are outlined.

The conversion of triosephosphate via methylglyoxal, a bypass to the glycolytic sequence in methylotrophic yeasts?

The conversion of triosephosphate via methylglyoxal, a bypass to the glycolytic sequence in methylotrophic yeasts?

The conversion of triosephosphate via methylglyoxal, a bypass to the glycolytic sequence in methylotrophic yeasts?

The conversion of triosephosphate via methylglyoxal, a bypass to the glycolytic sequence in methylotrophic yeasts?

Catabolic metabolism in Trypanosoma cruzi

Culture, blood and intracellular forms of Trypanosoma cruzi have a high rate of endogenous oxygen uptake and probably utilize amino acids and carbohydrates as their exogenous energy sources. It is likely that triglyceride is the main energy reserve. Oxidation of carbohydrate by all forms is probably via a glycolytic sequence and a complete tricarboxylic acid cycle. These data suggest that the substrates utilized and catabolic pathways present in mammalian forms of T. cruzi are similar to those of culture forms of the organism and are quite distinct from those of the bloodstream forms of African trypanosomes.

The effect of long-term arterial occlusion on energy metabolism of the human quadriceps muscle

The effect of 1.5 to 2.5 h tourniquet ischemia on energy metabolism of the quadriceps muscle was studied using percutaneous needle biopsy technique in sixteen patients operated on for an inveterated knee injury. During occlusion there was a moderate decrease in ATP with an increase in ADP and AMP. This change resulted in a decreased energy charge potential. At the same time phosphorylcreatine (PC) decreased markedly while creatine (Cr) increased giving a constant total creatine (TCr). An accumulation of lactate during occlusion with values up to 80 mmol/kg d.m. (dry muscle) was seen. A 15% reduction in glycogen was calculated. After release of the tourniquet the active phosphate concentration and the energy charge potential returned to basal levels within 5 min and most of the metabolites in the glycolytic sequence were also normalized. Muscle lactate content was normal after 30 min of intact circulation. The results suggest that longterm tourniquet ischemia induces marked changes in energy metabolism in skeletal muscle, but that the changes are rapidly and completely reversible with restoration of blood flow.

Erythrocyte membrane proteins in hereditary glucosephosphate isomerase deficiency.

Erythrocytes (approximately equal to 50% reticulocytes) obtained from a splenectomized patient with a thermolabile variant of glucosephosphate isomerase (GPI) deficiency showed a striking degree of crenation and decreased filterability through 3-micrometer Nuclepore filters (Nuclepore Corp., Pleasanton, Calif.). Membranes prepared by hypotonic lysis of such erythrocytes were found to contain a high molecular weight aggregate which was probably disulphide-bonded. The 10% most dense erythrocyte fraction showed an accentuation of aggregate formation while aggregates could not be detected in the 10% least dense erythrocyte fraction. The aggregate consisted mainly of spectrin (band 1) and a protein with the mobility of 4.2. "Extractability" of spectrin from these membranes was also markedly diminished. Incubation of the erythrocytes for 24 h in substrate-free medium caused more pronounced spectrin aggregation than in low or high reticulocyte controls. Incubation of low or high reticulocyte controls for 24 h in medium that contained glucose completely prevented the formation of the high molecular weight aggregate. GPI-deficient erythrocytes incubated with glucose in the medium showed an accentuation of membrane protein aggregate formation; however, this was almost completely reversed by the addition of adenine and inosine to the incubation medium or by the use of fructose, the intermediate just distal to the "block" in glycolysis, as the sole substrate. ATP and reduced glutathione levels in the GPI-deficient erythrocytes incubated with glucose were similar to that found in the low and high reticulocyte controls. Our findings suggest that only a proportion of erythrocytes (the older, more dense population of cells) are susceptible to the formation of disulphide-bonded aggregates, and that this is directly related to an impairment of substrate flow through the glycolytic sequence. The exact mechanism of aggregate formation in these erythrocytes remains to be elucidated.

The effect of long-term arterial occlusion on energy metabolism of the human quadriceps muscle.

The effect of 1.5 to 2.5 h tourniquet ischemia on energy metabolism of the quadriceps muscle was studied using percutaneous needle biopsy technique in sixteen patients operated on for an inveterated knee injury. During occlusion there was a moderate decrease in ATP with an increase in ADP and AMP. This change resulted in a decreased energy charge potential. At the same time phosphorylcreatine (PC) decreased markedly while creatine (Cr) increased giving a constant total creatine (TCr). An accumulation of lactate during occlusion with values up to 80 mmol/kg d.m. (dry muscle) was seen. A 15% reduction in glycogen was calculated. After release of the tourniquet the active phosphate concentration and the energy charge potential returned to basal levels within 5 min and most of the metabolites in the glycolytic sequence were also normalized. Muscle lactate content was normal after 30 min of intact circulation. The results suggest that longterm tourniquet ischemia induces marked changes in energy metabolism in skeletal muscle, but that the changes are rapidly and completely reversible with restoration of blood flow.

Metabolism of Red Blood Cells in Chronic Renal Failure

This paper starts a series on red blood cell (RBC) metabolism in patients with chronic renal failure (CRF). The glycolytic enzyme levels and in vitro half-lives of these patients' RBCs were determined. A number of enzymes (hexokinase, glucose-6-phosphate isomerase, fructose-6-phosphate kinase, aldolase, glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase) showed higher activities than in normal control RBCs. Other enzyme activities were normal. These results were discussed and several possible mechanisms considered. We favour the point of view of a shortened life span of the RBCs in CRF, making the most unstable enzymes of the glycolytic sequence appear increase as compared with normal controls.

The stability of lactic acid production in resting suspensions of Lactobacillus delbrueckii

AbstractThe stability of resting glycolytic activity (RGA) i.e. lactic acid production from glucose, in non‐growing suspensions of Lactobacillus delbrueckii was examined. Non‐growing conditions were imposed by removal of essential nutrients or by the addition of antibiotics. The stability of RGA was reduced in fast‐grown chemostat cells. Mg2+, reducing agents, the rigorous exclusion of oxygen and a constant supply of energy source gave a five‐fold increase in RGA and a 25‐fold increase in stability in cells deprived of a nitrogen source. Glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) activity severely limited RGA after about 8 h of incubation. No evidence of excessive ATP accumulation or ADP depletion was found. Addition of chloramphenicol, actinomycin D or mitomycin C decreased RGA stability over a 24‐h period. Addition of yeast extract and tryptone to a mixture containing phosphate, Mg2+, thioglycollate and chloramphenicol gave a three‐fold increase in RGA which lasted for about 1 h. Mg2+ is believed to stimulate the glycolytic sequence directly and oxygen probably inhibits GAPDH by interaction with the ‐SH groups of the enzyme. Tryptone and yeast extract probably stimulate pyruvate kinase activity, and this enzyme is also absolutely dependent on fructose‐1, 6‐diphosphate for activity.

In vivo regulation of glycolysis and characterization of sugar: phosphotransferase systems in Streptococcus lactis.

Two novel procedures have been used to regulate, in vivo, the formation of phosphoenolpyruvate (PEP) from glycolysis in Streptococcus lactis ML3. In the first procedure, glucose metabolism was specifically inhibited by p-chloromercuribenzoate. Autoradiographic and enzymatic analyses showed that the cells contained glucose 6-phosphate, fructose 6-phosphate, fructose-1,6-diphosphate, and triose phosphates. Dithiothreitol reversed the p-chloromercuribenzoate inhibition, and these intermediates were rapidly and quantitatively transformed into 3- and 2-phosphoglycerates plus PEP. The three intermediates were not further metabolized and constituted the intracellular PEP potential. The second procedure simply involved starvation of the organisms. The starved cells were devoid of glucose 6-phosphate, fructose 6-phosphate, fructose- 1,6-diphosphate, and triose phosphates but contained high levels of 3- and 2-phosphoglycerates and PEP (ca. 40 mM in total). The capacity to regulate PEP formation in vivo permitted the characterization of glucose and lactose phosphotransferase systems in physiologically intact cells. Evidence has been obtained for "feed forward" activation of pyruvate kinase in vivo by phosphorylated intermediates formed before the glyceraldehyde-3-phosphate dehydrogenase reaction in the glycolytic sequence. The data suggest that pyruvate kinase (an allosteric enzyme) plays a key role in the regulation of glycolysis and phosphotransferase system functions in S. lactis ML3.

Enzymatic basis for bioenergetic differences of alveolar versus peritoneal macrophages and enzyme regulation by molecular O2.

Alveolar macrophages (AM) and peritoneal macrophages (PM) originate from common precursor cells, but function in different O2 environments. In the present studies, the impact of different O2 tensions on cell metabolism has been quantitatively determined, an enzymatic basis for these differences established, and a mechanism which regulates enzymatic differences demonstrated. O2 consumption and lactate production were compared in rabbit AM and PM in air and nitrogen. In air, AM demonstrate significantly greater O2 utilization. In nitrogen, (where glycolysis is the major source of energy provision) lactate production is two- to threefold greater in the PM. A comparison of several enzymes of energy metabolism in AM and PM indicate that one basis for the differences in cell energetics is a difference in activity of key enzymes of both the oxidative phosphorlyative and the glycolytic sequences. Exposure of cultivated AM to hypoxic conditions results in changes in the activity of these enzymes such that the AM closely resembles the PM. A key enzyme in oxidative phosphorylation (cytochrome oxidase) shows decreased activity and reaches values similar to those found in the PM. A key enzyme in glycolysis (pyruvate kinase) shows increased activity to values resembling those found in the PM. These alterations in enzyme pattern occur in isolated cell systems, suggesting that molecular O2 modifies the intrinsic cellular regulation of some enzymes of energy metabolism. Alterations in O2 tension may lead to alterations of the rate of biosynthesis and (or) the rate of biodegradation of key enzymes involved in oxidative phosphorylation and glycolysis. In turn, the alteration of enzyme patterns leads to a more suitable bioenergetic pattern as a function of O2 availability.

Cerebral carbohydrate metabolism during acute carbon monoxide intoxication

The cerebral metabolic effects of 2.5, 5, 7.5, 10, 20, 30 and 60 min exposure to 1% CO were studied in lightly anesthetized rats by measurement of cerebral cortical contents of selected glycolytic and citric acid cycle intermediates, as well as tissue energy phosphates. The initial change in the glycolytic sequence occurred at 2.5 min with decreases in tissue glucose and glucose-6-phosphate and increases in fructose-1,6-diphosphate which indicated an activation of phosphofructokinase and hexokinase. The “crossover” pattern between glucose-6-phosphate and fructose-1,6-diphosphate was present at 5, 7.5 and 10 min, but not at 20, 30 and 60 min and thus confirmed previous observations that detection of phosphofructokinase activation in acute unifactorial cerebral hypoxia requires tissue study during the early phases of the experimental exposure. The initial activation of phosphofructokinase occurred in the absence of detectable changes in the tissue content of ATP, ADP, AMP or phosphocreatine and therefore suggested that an imbalance of tissue energy homeostasis is not a prerequisite for the activation of glycolysis in CO intoxication. One percent CO resulted in an increasing malate/oxaloacetate ratio at 5 min, followed by a decrease in α-ketoglutarate and aspartate at 7.5 min which suggested a shift in the aspartate aminotransferase reaction towards the replenishment of oxaloacetate removed via the malate dehydrogenase reaction. Subsequent increases in α-ketoglutarate at 10, 20, 30 and 60 min were associated with increases in alanine, indicating a contributing role for a secondary shift of the alanine aminotransferase reaction in the replenishment of α-ketoglutarate. A comparison of the CO induced changes in the glycolytic and citric acid cycle pathways with those seen in acute hypoxemia indicates no basic qualitative differences in the metabolic responses of brain tissue to the two conditions.

Negative interaction of orthophosphate with glycolytic metabolism by Streptococcus mutans as a possible mechanism for dental caries reduction

Orthophosphate (Pi) interacted in a negative way with the binding of the allosteric activator, fructose-1,6-diphosphate, to the lactate dehydrogenase from all strains of Streptococcus mutans studied The interaction of Pi with the enzyme served markedly to increase the [M] 0.5 v value for fructose-1,6-diphosphate. The negative interaction of Pi with the terminal regulatory enzyme in the glycolytic sequence may provide a mechanism by which high Pi levels in the extracellular environment decrease the rate of acid production from exogenous carbohydrates by oral isolates of Strep. mutans and may also explain, at least in part, why increased Pi levels in the diet serve to reduce the incidence of dental caries.

Factors Affecting the Rate of Lactate Production in Rat Lens

The rate of lactate production from various glycolytic intermediates was tested with a dispersed lens incubating system. Conditions required to establish maximal linear activity (lactate production vs. time) in each case was examined. It was confirmed that under noninhibitory concentrations of ATP, hexokinase paced glycolysis. At pH 7.05, the glycolytic rate was 40% of that at pH 7.43 (37.5°C); pH variations affected early but not late steps of glycolytic sequence. In aging lenses, the glycolytic rate (based on lens wet weight) was reduced to 52% of young lenses; furthermore, phosphofructokinase in old lenses seemed to have partially lost its capacity to phosphorylate fructose-6-phosphate.