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PubMed1987

Malarial parasite hexokinase and hexokinase-dependent glutathione reduction in the Plasmodium falciparum-infected human erythrocyte.

The metabolism of glucose in Plasmodium falciparum-infected human erythrocytes is increased 50- to 100-fold. This is accomplished in part by parasite-directed synthesis of a protozoan hexokinase with unique kinetic, electrophoretic, and heat stability properties. The total hexokinase activity is increased approximately 25-fold over that of control uninfected erythrocytes of the same age from the same donor. The parasite hexokinase has a lower affinity for glucose than the mammalian enzyme (Km = 431 microM +/- 21 S.D. for the parasite enzyme versus 98 microM +/- 10 for the erythrocyte enzyme), but the Km for ATP and the Vmax for both glucose and ATP are similar. The NADPH-dependent reduction of oxidized glutathione (GSSG) requires the formation of glucose 6-phosphate which in turn is metabolized by the pentose shunt pathway in which NADPH is generated. Using glucose as the substrate, lysates of P. falciparum-infected normal erythrocytes demonstrated enhanced ability to reduce GSSG. The rate of GSSG reduction was proportional both to the parasitemia and the hexokinase activity of the lysates. However, infected glucose-6-phosphate dehydrogenase-deficient red cell lysates displayed a severely restricted ability to reduce GSSG under the same conditions. In conclusion, P. falciparum-infected red cells contain a parasite-encoded hexokinase with unique properties which initiates the large increase in glucose consumption. In normal infected red cells, reduction of GSSG is also dependent upon hexokinase activity, but in infected glucose-6-phosphate dehydrogenase-deficient red cells, the absence of this pentose shunt enzyme remains the rate-limiting step in GSSG reduction.

Adenosine Triphosphate↗

PubMedDate not supplied

[Effect of carbon sources on the biosynthesis of ergot alkaloids and the activity of carbon metabolism enzymes in Penicillium sizovae].

The study was aimed at finding out how different carbon sources influenced the growth of Penicillium sizovae, the biosynthesis of epoxyagroclavine-1 and agroclavine-1 as well as the activity of key enzymes involved in the citric acid cycle, the pentose phosphate pathway and the glyoxylate cycle. The fungal growth was shown to depend on the carbohydrate substrate: it had a two-phase profile when P. sizovae was cultivated on mannitol and glucose, but not on sorbitol. The quantitative content and composition of ergoalkaloids depended on the combination of carbohydrate and organic acid substrates. The overall productivity of the mycelium (epoxyagroclavin-1+agroclavin-1) was highest when mannitol and fumarate were used. A medium with sorbitol and fumaric acid was very selective in terms of epoxyagroclavine-1 synthesis. The high level of alkaloid biosynthesis correlated with the active functioning of the pentose phosphate cycle and with the low activity of the CAC.

Carbon↗

PubMedDate not supplied

[Role of adrenergic mechanisms in regulating memory engram retrieval and energy metabolism in the brain structures of the rat].

In conditions of stimulation of adrenergic mechanisms with ephedrine, there was an improvement of the memory engrams reproduction (MER). Blockade of the alpha-adrenergic system by pyrroxan more expressively impeded reproduction of a passive defensive habit in comparison with the action of a beta-adrenolytic, the obsidan. Stimulation of MER processes was accompanied by a parallel activation of glucose-6-phosphate- and 6-phosphategluconatedehydrogenases of pentose path in the tissues of the frontal area of the cerebral cortex and pons Varolii. Blockade of alpha-adrenoreceptors suppressed the activity of the given enzymes in the same structures, while the obsidan suppressed the dehydrogenases of the pentose path only in the frontal zone of the neocortex.

Animals↗

PubMed1985

[Chemical composition of a preparation of the cell walls of Corynebacterium diphtheriae].

The chemical characteristics of 6 batches of the preparation, obtained from the cell wall of C. diphtheriae grown in liquid and solid culture media, with respect to their content of nitrogen, hexoses, pentoses, total amino sugars, lipids and to the possible admixture of nucleic acids are presented. From the results of the chemical analysis of these batches their standardization according to the ratio of total amino sugars and pentoses to total nitrogen in C. diphtheriae cell-wall preparation is proposed.

Cell Wall↗

PubMed1985

Enzyme histochemical features of equine gluteus muscle fibers.

Gluteal muscle specimens were taken from 4 horses. From 1 of the 4 gluteal muscles, serial sections were prepared. Individual muscle fibers were identified and studied, using photomicrographs of sections stained by different enzyme histochemical methods. In specimens in which cytoplasmic soluble enzymes were studied, use was made of the semi-permeable membrane technique to hamper enzyme diffusion into reaction fluids. Enzymes involved in glycogenolysis, glycolysis, the tricarboxylic acid cycle, synthesis of reduced nicotinamide adenine dinucleotide phosphate, the pentose phosphate cycle, the alpha-glycerolphosphate shuttle, the respiratory chain, catabolism, and muscular contraction were studied. Some key enzymes of different metabolic pathways were also included. Each of 3 fiber types identified had distinct features. Type I fibers were characterized by a relatively strong aerobic capacity, compared with type IIA fibers, which were more glycolytic and had strong aerobic and moderate-to-strong anaerobic capacity. Type IIB fibers were characterized by a relatively low aerobic and a relatively high anaerobic capacity, and were glycolytic. Activities of phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, and alpha-naphtylesterase (nonspecific esterase) were so markedly different in the 3 fiber types that fiber typing was possible, aided by the demonstration of the activities of these enzymes. In type IIB fibers, the pentose phosphate cycle was more important than in the other fiber types. Except for the unexplained high alpha-naphtylesterase activity in type IIB fibers, catabolic enzymes were not active in healthy equine muscle fibers.

Animals↗

PubMed1975

[Age-related changes in the content and characteristics of glycosaminoglycans in human aortas].

The vascular wall is rich in glucoseaminglicanes (GAG), which form the basic intercellular substance and determine its multiple functions. Using analytic and chromatographic methods the author examined hexauronic acid (HA), pentoses (P), sulphate groups and various derivatives of GAG (hyaluronic acid (HA), pentoses (P), sulphate groups and various derivatives of GAG (hyaluronic acid (HA), dermatan-sulfate (DS), keratansulfate (KS), chondroitinsulfate (HS), and cheransulfate (HES) in human aorta, obtained from persons at the age of 10 and over 70 years of age. Ten aortas of each group were examined. The studies showed that in the aortas of the adult persons the content of HA, P, HS, KS and sulphate groups was considerably higher than that of the aourtas, obtained form the young persons. There was an impression that the adult factor affected substantialy the qualitative characteristics of GAG--with advancement of age the lenght of polysaccharide chains was shortened and the degree of sulphatation was increased. The accumulation of acid GAG in the aorta of adult persons impaired the metabolism of substances between blood and tissue, which enhanced the infiltration of the blood vessels with lipids and proteins, especialy when there was a blood increase in their content (hyperlipemia, hypercholesterinemia, ect.)

Age Factors↗

PubMed1972

Identification of a xylose-containing cerebroside in the salt gland of the herring gull.

A pentose-containing cerebroside has been identified in the salt gland of the herring gull, using mass spectrometry of acetyl and trimethylsilyl derivatives. A detailed interpretation of the spectra allowed a conclusion concerning the major long-chain base (the C(20) homolog of sphingosine) and the major fatty acids (C(22)-C(25) 2-hydroxy fatty acids), using reference spectra of synthetic galactosylceramides. A six-membered glycose ring (aldopyranose) was demonstrated by mass spectrometry of the acetyl derivative of periodic acid-oxidized and sodium borodeuteride-reduced pentosylceramide. By gas-liquid chromatography and mass spectrometry of methanolysis products, the pentose was shown to be identical with xylose. The procedures were applied to 25-50 micro g of glycolipid.

Animals↗

PubMed1970

Inhibition of lipid synthesis and glucose-6-phosphate dehydrogenase in rat skin by dehydroepiandrosterone.

Lipid synthesis from acetate-1-(14)C by rat skin was inhibited 44-56% by 2.5 x 10(-4) m dehydroepiandrosterone (DHA) in vitro with or without addition of glucose in the incubation medium. This inhibition affected all the lipid fractions examined (hydrocarbons, sterols, sterol esters, tri-, di- and monoglycerides, fatty acids, and polar lipids) and could be reversed by NADPH. DHA also inhibited lipid synthesis from glucose-U-(14)C and the formation of (14)CO(2) from glucose-1-(14)C, indicating interference with pentose cycle activity. Experiments with the 105,000 g supernatant fluid of rat skin homogenates demonstrated considerable activities of malic enzyme (ME) (12.6 nmoles of NADPH generated per min per mg of protein), of glucose-6-phosphate dehydrogenase (G6PD), and of 6-phosphogluconate dehydrogenase (6PGD) (17.5 nmoles of NADPH generated per min per mg of protein). G6PD was inhibited 98% by 2.5 x 10(-4) m dehydroepiandrosterone, while 6PGD and ME were not affected. It can be estimated from these data that the pentose cycle may contribute 41-57% of the NADPH needed for lipid synthesis in rat skin; the remainder of the necessary NADPH is presumably supplied by malic enzyme.

Acetates↗

PubMed1979

The breakdown of adenine nucleotides in glucose-depleted human red cells.

1) The rate of 2,3-bisphosphoglycerate breakdown is independent of pH value. 2) The adenine nucleotide pattern at alkaline pH values with its characteristic lowering of ATP and the accompanying accumulation of fructose-1,6-bisphosphate is caused by a relative excess of the activity of the hexokinase-phosphofructokinase system as compared wity pyruvate kinase. 3) The breakdown of adenine nucleotides proceeds via AMP mainly through phosphatase and not via AMP deaminase. 4) The constancy of the sum of nucleotides as long as glucose is present is postulated to be due to resynthesis via adenosine kinase which competes successfully with adenosine deaminase. 5) A procedure is given to calculate ATPase activity of glucose-depleted red cells. The results indicate that the ATPase activity is less at lower pH values and declines with time. An ATPase with a high Km for ATP is postulated. 6) During glucose depletion ATP production is mostly derived from the breakdown of 2,3-bisphosphoglycerate and the supply from the pentose phosphate pool both of which proceed at a constant rate. The contribution of pentose phosphate from the breakdown of adenine nucleotides amounts to 40% of the lactate formed at pH 6.8 and is about twice the lactate at pH 8.1.

Adenine Nucleotides↗

PubMed1979

The effect of oxygen and paraquat on the 14C-glucose oxidation of rabbit alveolar macrophages and lung slices.

In this study, we measured the effects of different concentrations of paraquat (0,01 mM and 1,0 mM) on the 1-14CO2 and 6-14CO2 production of rabbit lung slices and isolated alveolar macrophages, in 20% and 95% oxygen phases respectively. A 95% oxygen phase induced an increase in the 6-14C-glucose oxidation of contorol lung slices over a 3-hour period, while the increased activity of the pentose pathway over the first 2 hours started to decline during the third hour of incubation. Paraquat (1,0 mM) in 20% oxygen caused a consistent increase in the 6-14CO2 production by lung slices, but in a 95% oxygen phase gradually inhibited the 6-14C-glucose oxidation over a period of 3 hours. The pentose phosphate pathway was highly significantly stimulated by 1,0 mM paraquat in 20% and 95% oxygen over 3 hours. When isolated alveolar macrophages (viability 95%) were incubated in a 20% and a 95% oxygen phase respectively, both the 6-14C-glucose and 1-14C-glucose oxidation rates were significantly inhibited by 1,0 mM paraquat after 1 hour. Our results confirmed the initial increase in glycolytic metabolism induced by paraquat, but also inhibited by paraquat when lung slices were incubated in a 95% oxygen phase. The fact that the glucose metabolism in alveolar macrophages is more sensitive to paraquat exposure than that of cells in lung slices may be related to the genesis of the intra-aveolar pulmonary lesions described in the literature.

Animals↗

PubMed1979

Insulin insensitivity and altered glucose utilization in cultured rat adipose tissue.

Glucose utilization was studied in isolated fat cells prepared from rat adipose tissue which had been cultured for 18 hr in TC 199 medium. When 1% bovine serum albumin (BSA) was in the culture medium, basal rates of (14)CO(2) and [(14)C]triglyceride production from [1-(14)C]glucose were markedly depressed and there was no effect of insulin. With 4% BSA, basal (14)CO(2) production was the same as in cells prepared from fresh tissue and basal triglyceride production was greatly increased. Insulin effect on these cells was minimal. One-minute uptake of [(14)C]2-deoxyglucose was stimulated by 800-1000% in fresh cells and 300-500% in cells cultured with either 1% or 4% BSA. Oxidation of [U-(14)C]glucose showed a much smaller impairment in cultured cells than for [1-(14)C]glucose, suggesting that the pentose phosphate shunt was more severely impaired than glycolysis. Glyceride-glycerol production was increased in cultured cells relative to preculture (fresh) cells. There was no effect of insulin in the culture medium in any of these systems. Rates of free fatty acid and glycerol release were markedly increased in cultured cells, especially when insulin was present in the culture medium. The acute antilipolytic effect of insulin was retained, so that insulin in the test incubation decreased lipolysis by 40-80%. Nevertheless, cell-associated fatty acids were increased in cultured cells and FFA/albumin ratios in the medium often reached potentially toxic levels. The reduction in pentose phosphate shunt activity, lipogenesis, and insulin effect resembles other models of insulin insensitivity. The impaired metabolism is probably due to an intracellular defect. A possible toxic role of either intracellular or extracellular fatty acids cannot be excluded. This system should be a useful model in which to study the cellular mechanisms of insulin insensitivity in adipocytes.-Bernstein, R. S. Insulin insensitivity and altered glucose utilization in cultured rat adipose tissue.

Animals↗

PubMed1983

Muscarinic receptor binding and oxidative enzyme activities in the adult rat superior cervical ganglion: effects of 6-hydroxydopamine and nerve growth factor.

Administration of 6-hydroxydopamine to adult rats results in changes in the superior cervical ganglion similar to those noted after axotomy; namely, a decrease in muscarinic receptor binding and increases in activities of the oxidative enzymes of the pentose phosphate pathway. These changes were either prevented or attenuated markedly by the systemic administration of nerve growth factor. Administration of nerve growth factor alone did not significantly increase N-methylscopolamine binding in the ganglion or reduce the activities of the oxidative enzymes. Explants of the ganglion maintained in serum-free medium over a period of 3 days demonstrated increases in oxidative enzyme activity and a decrease in N-methylscopolamine binding. Addition of 20 nM nerve growth factor to the culture medium prevented the decline in N-methylscopolamine binding in ganglion explants. The increases in oxidative enzyme activities were unaltered. Addition of high amounts of nerve growth factor, 200 nM, resulted in a significant increase in tyrosine hydroxylase activity but no further increase in N-methylscopolamine binding in ganglion explants. Glucocorticoids added to the culture medium did not affect the muscarinic binding or enzyme activities. Thus, decreases in muscarinic binding activity which occur in the superior cervical ganglion after axotomy or 6-hydroxydopamine treatment may be explained by a loss of nerve growth factor supplied to the ganglion. Increases in the oxidative enzymes of the pentose phosphate pathway that occur in the ganglion after axonal injury appear to involve additional factors.

Animals↗

PubMedDate not supplied

[Carbon dioxide fixation and its regulation in Synechococcus (Anacystis nidulans) cyanobacteria].

The bulk of 14CO2 assimilated in photosynthesis by the growing culture of Synechococcus was incorporated in the cell via the reductive pentose phosphate cycle. Up to 70% of the label was incorporated into phosphoglyceric acid and phosphoric esters of sugars at all stages of the active cultural growth after 1 min of exposition in the light in the presence of NaH14CO3. The relative proportion of the label in phosphorylated compounds of the reductive pentose phosphate cycle decreased if the exposition was increased to 20 min. The content of 14C in aspartic acid did not exceed 9%. In the presence of nucleotide peptide (NP) isolated from Anabaena variabilis, the overall rate of carbon dioxide assimilation rised by 50% as compared to the control by the fourth day of the growth. The specific rate of 14CO2 assimilation hardly changed within four days of the cultural growth; it was 44 nmole/min/mg, or 55 nmole/min/mg in the presence of NP. NP had no effect on the qualitative composition of the products of photosynthesis; however, the percentage of sugar phosphates, phosphoenolpyruvate and organic acids (carbohydrates at the stage of exponential growth) in these products increased in the presence of NP (exposition for 20 min). The percentage of carbohydrates was found to change only slightly as compared to the control in the presence of NP. The content of protein and RNA increased by 25-30% and the content of DNA by 60%. The action of NP was most pronounced if the content of DNA was calculated per cell. Therefore, there is a correlation between the content of DNA and the intensification of carbon dioxide fixation by the culture.

Bacterial Proteins↗

PubMed1984

[Correlation between the rate of protein and nucleic acid synthesis and the intensity of various glucose metabolic pathways in rat liver cells].

A sharp and strong suppression of protein synthesis by cycloheximide in liver cells of starving rats is paralleled with activation of RNA synthesis and glucose-6-phosphate dehydrogenase production. Subsequent reconstitution and stimulation of protein synthesis (6-12 hrs after cycloheximide injection) result in activation of hexokinase. Upon stimulation of DNA synthesis (48-60 hrs after cycloheximide injection) the activity of both enzymes is very low. Since glucose-6-phosphate dehydrogenase appears to be the limiting step of glucose decay via the pentose phosphate pathway, and hexokinase is the limiting step of glycolysis, it was assumed that RNA synthesis predominantly occurs via the pentose phosphate pathway, while that of proteins via glycolysis.

Animals↗

PubMed1982

The mechanism of the insulin-like effects of ionic zinc.

The insulin-like effects of ionic zinc (Zn2+) were studied in isolated rat adipocytes. Concentrations of Zn2+ between 250 and 1000 microM stimulated 3-O-methylglucose transport and glucose metabolism to CO2, glyceride-fatty acid, and glyceride-glycerol. Selective stimulation of the pentose phosphate cycle was observed since a Zn2+-induced increase in glucose carbon 1 oxidation persisted even when glucose transport was blocked with 50 microM cytochalasin B or when transport was no longer rate-limiting for metabolism at high concentrations of glucose. Enhanced pentose phosphate cycle activity may have been due to a selective inhibition of glutathione reductase by the ion, which was also accompanied by a fall in cellular glutathione content. Zn2+ also inhibited lipolysis stimulated by the beta-adrenergic agent ritodrine in the absence of glucose. The effects of Zn2+ on glucose oxidation and stimulated rates of lipolysis were inhibited by extracellular catalase, indicating that they were largely a result of H2O2 generation. The H2O2 production appeared for the most part to be caused by zinc-catalyzed autoxidation of sulfhydryl groups present on external cell membranes, although involvement of sulfhydryl groups on bovine serum albumin in the buffer could also have contributed. The insulin-like effects of Zn2+ in adipocytes are therefore caused not only by direct effects of the ion on intracellular metabolism but also by indirect effects related to H2O2 generation.

3-O-Methylglucose↗

PubMed1980

[Dehydroepiandrosterone deficiency in psoriasis. Hypothesis on the etiopathogenesis of this disease].

In patients with psoriasis in extra- and intracellular deficiency of dehydroepiandrosterone can be demonstrated which leads to an activation of the pentose-phosphate cycle. This dehydroepiandrosterone deficiency is caused by an increased intracellular activity of 17 beta-hydroxysteroid-dehydrogenase. This results in an increased formation of the reduction product androstendiol, which is unable to inhibit the glucose-6-phosphate dehydrogenase, the keye enzyme of the pentose-phosphate cycle. In addition, a decreased penetration of the steroid through the membrane of erythrocytes is demonstrable, by which the intracellular deficiency of dehydroepiandrosterone is still augmented. The effects of this dehydroepiandrosterone deficiency are changes in the humoral regulation of events in growth and proliferation in patients with psoriasis.

17-Hydroxysteroid Dehydrogenases↗

PubMed1980

Protein utilization in correlation to energy intake.

The effect of 14 days' intake of mounting quantities of fats and energy on a constant optimum utilizable amount of dietary protein was studied in weaned rats weighing 60 g. Growth (PER, NPR) and utilization (NPU--body, LPU--liver) parameters of biological protein value were determined, supplemented by a study of the course of the antithetical processes of gluconeogenesis and glycolysis, of the pentose cycle, the citric acid cycle and of transamination processes in the animals' liver. According to the maximum PER, NPR, NPU and LPU values, a 14 days' intake of 59.2 g fats and 4.518 MJ, corresponding to a diet containing 10% protein, 30% fat and 2.274 MJ, had the best effect on the optimum utilizable amount of casein (21 g/14 days). A diet containing 35% and 40% fat stimulated gluconeogenesis, followed by a transamination process and inhibition of glycolysis, the citric acid cycle and lipogenesis (depression of pentose cycle activity and a decrease in the amount of body fat), and simultaneously reduced the values of all four parameters of protein biological value. The results demonstrate that very best diet for newly weaned rats is one containing 10% high quality protein, 30% fat and 2.274 MJ.

Animals↗

PubMed1983

[Biosynthesis of levorin and activity of several enzyme systems of Streptomyces levoris depending on culture conditions].

The regularities of changes in the main oxidation-reduction enzymes of the tricarboxylic acid cycle (TAC) and the pentose cycle were studied under different cultivation conditions: with the use of the control soybean-corn-hydrol medium and the medium with addition of a biostimulant produced by C. tropicalis. It was shown that the activity levels of the dehydrogenase systems of the TAC and the pentose cycle of S. levoris grown in the presence of the biostimulant were higher. The increase in the production levels of levorin due to addition of the biostimulant was connected with the activity of the systems responsible for regeneration of NADP.H2.

Antifungal Agents↗