Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PENTOSES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed1990

Biosynthesis of Poly-beta-Hydroxyalkanoates from Pentoses by Pseudomonas pseudoflava.

The potential of Pseudomonas pseudoflava to produce poly-beta-hydroxyalkanoates (PHAs) from pentoses was studied. This organism was able to use a hydrolysate from the hemicellulosic fraction of poplar wood as a carbon and energy source for its growth. However, in batch cultures, growth was inhibited completely at hydrolysate concentrations higher than 30% (vol/vol). When P. pseudoflava was grown on the major sugars present in hemicelluloses in batch cultures, poly-beta-hydroxybutyric acid (PHB) accumulated when glucose, xylose, or arabinose was the sole carbon source, with the final PHB content varying from 17% (wt/wt) of the biomass dry weight on arabinose to 22% (wt/wt) of the biomass dry weight on glucose and xylose. Specific growth rates were 0.58 h on glucose, 0.13 h on xylose, and 0.10 h on arabinose, while the specific PHB production rates based on total biomass ranged from 0.02 g g h on arabinose to 0.11 g g h on glucose. PHB weight-average molecular weights were 640,000 on arabinose and 1,100,000 on glucose and xylose. The absolute amount of PHB in the cells decreased markedly when nitrogen limitation was relaxed by feeding ammonium sulfate at the end of the PHB accumulation stage of the arabinose and xylose fermentations. Copolymers of beta-hydroxybutyric and beta-hydroxyvaleric acids were produced when propionic acid was added to shake flasks containing 10 g of glucose liter. The beta-hydroxyvaleric acid monomer content attained a maximum of 45 mol% when the initial propionic acid concentration was 2 g liter.

Journal Article↗
PubMed1991

Isolation and characterization of Escherichia coli mutants able to utilize the novel pentose L-ribose.

Wild-type strains of Escherichia coli were unable to utilize L-ribose for growth. However, L-ribose-positive mutants could be isolated from strains of E. coli K-12 which contained a ribitol operon. L-ribose-positive strains of E. coli, isolated after 15 to 20 days, had a growth rate of 0.22 generation per h on L-ribose. Growth on L-ribose was found to induce the enzymes of the L-arabinose and ribitol pathways, but only ribitol-negative mutants derived from strains originally L-ribose positive lost the ability to grow on L-ribose, showing that a functional ribitol pathway was required. One of the mutations permitting growth on L-ribose enabled the mutants to produce constitutively an NADPH-linked reductase which converted L-ribose to ribitol. L-ribose is not metabolized by an isomerization to L-ribulose, as would be predicted on the basis of other pentose pathways in enteric bacteria. Instead, L-ribose was metabolized by the reduction of L-ribose to ribitol, followed by the conversion to D-ribulose by enzymes of the ribitol pathway.

Aldose-Ketose Isomerases↗
PubMed1983

Pentose phosphate shunt, pyridine nucleotides, glutathione, and insulin secretion of fetal islets.

In rat fetal islets it was tested whether their failure to respond to glucose with insulin secretion might be due to inadequate changes of the redox state of pyridine nucleotides and of glutathione. In islets of newborn (5 days) and adult (3 mo) rats elevation of glucose produced an increase in insulin secretion, pentose phosphate shunt (PPS) activity, and NADPH/NADP, NADH/NAD, and GSH/GSSG ratios. An increase in the NADH/NAD ratio was also observed in islets of fetal rats, but in contrast to islets of newborns and adults no increase in insulin release, PPS activity, and the GSH/GSSG ratio was observed. However, at all glucose concentrations tested islets of fetal rats exhibited a high NADPH/NADP ratio similar to the ratio of adult rats in the presence of 16.7 mM glucose. It is suggested that in fetal islets there exists a lack of hydrogen transfer from NADPH to GSSG. The high NADPH/NADP ratio may in turn suppress PPS activity. It is possible that the missing insulin release of fetal islets in response to glucose is at least in part due to the fact that the oxidation-reduction state of the GSH/GSSG system also does not respond to the elevation of the glucose concentration.

Animals↗
PubMed1980

The pentose phosphate pathway in brain during development.

Sprague-Dawley rats were delivered in our laboratory and decapitated at ages varying between 1 and 60 days. The concentrations of 6-phosphogluconate in extracts of the brain were determined in these litters and in adult rats. The highest of 6-phosphogluconate was seen in brains of 3-day-old rats when it was at that age more than six times the adult level. Turnover rates for this same compound were determined by an in vitro technique at ages 1, 3 and 12 days and in the adult. We conclude that the pentose phosphate pathway is more active in rat brain during early development than in the adult, with a peak occurring at 3 days of life, indicating a possible link to nucleic acid synthesis.

Aging↗
PubMed1981

Age-related changes in enzymes of rat brain. 1. Enzymes of glycolysis, the pentose phosphate pathway and lipogenesis.

Measurements have been made of the activity of the enzymes of the glycolytic, pentose phosphate and lipogenic pathways and of some marker enzymes of the tricarboxylic acid cycle in brains of rats aged between 20 days and 24 months. In general, the activity of the most enzymes measured was unchanged by aging but exceptions to this were increases of hexokinase, glucose-6-phosphate dehydrogenase and 'malic enzyme' and decreases of ATP-citrate lyase, acetyl-CoA carboxylase and fatty acid synthetase. An exceptionally large (2-fold) increase in the activity of cytosolic glycerol 3-phosphate dehydrogenase was noted. These changes are considered in relation to the overall metabolic activity of the brain.

Aging↗
PubMed1976

[A study of heterogeneity of isomerase and epimerase of pentose phosphates from rat spleen by electrophoresis in polyacrylamide gel].

The heterogeneity of isomerase and epimerase of pentose phosphates from rat spleen was studied by electrophoresis in polyacrylamide gel. Three electrophoretical fractions of the enzymes are demonstrated. The ten-fold purification of the isomerase and epimerase by saline fractionation does not alter their catalytic properties and electrophoretic pattern.

Animals↗
PubMed1975

[Pentose phosphate pathway and nucleic acid synthesis in human funicular tissue. In vitro studies].

Umbilical cord slices were incubated with either 1- or 6-14C-glucose, the radioactivities of which were measured in CO2 evolved. The ratio, 1 CO2/6 CO2 was low, being comprised between 1 and 2. Furthermore, this incubation of cord slices with tritiated uridine or thymidine resulted in very low incorporations, especially for the latter. Therefore, both the pentose phosphate pathway and the synthesis of nucleic acid have a low activity in the cord tissue: these might be signs of senescence in this otherwise fetal organ.

Carbon Dioxide↗
PubMed1990

[Pentose phosphate pathway in neuromuscular diseases--evaluation of muscular glucose 6-phosphate dehydrogenase activity and RNA content].

There have been several reports concerning elevated glucose 6 phosphate dehydrogenase (G6PDH), the rate-limiting enzyme of pentose phosphate pathway (PPP), in experimental muscle disturbances. PPP produces ribose, a substrate of RNA, and NADPH which is a cofactor of fatty acid synthesis. PPP also has a role of by-path pathway of glycolysis. Then, we evaluated G6PDH activity and RNA content in biopsied quadriceps muscle. The subjects were muscles from 23 neurogenic amyotrophy, 54 myopathy including 19 progressive muscular dystrophy (PMD), and 10 controls whose muscle was obtained at orthopedic surgery. Neurogenic amyotrophy consisted of 12 amyotrophic lateral sclerosis (ALS), 4 spinal muscular atrophy and 7 peripheral nerve disorders. Myopathy were 3 Duchenne dystrophy, 2 congenital muscular dystrophy, 8 limb-girdle type dystrophy, 6 facio-scapular +-humeral muscular dystrophy, 6 myotonic dystrophy, 6 mitochondrial myopathy, 5 endocrinological myopathy, 3 hypokalemic myopathy, 8 polymyositis and 4 other inflammatory myopathy. The assays of G6PDH and RNA were performed after Glock's and Fleck's methods, respectively. The control values were 3.6 +/- 0.8 nmol formed NADPH/mg protein/min (M +/- SD) in G6PDH and 0.69 +/- 0.17 micrograms/mg non-collagen protein in RNA. Most cases of PMD, as well as some cases of ALS, hyperthyroidism, mitochondria hypokalemic myopathy, inflammatory myopathy showed increased values (beyond M + 2SD of control) both in G6PDH and RNA. There were significant positive correlations between G6PDH activity and RNA content in PMD and motor neuron disease. Myotonic dystrophy showed normal values in both G6PDH and RNA. Half number of cases of mitochondrial myopathy demonstrated increased G6PDH alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1979

[Activities of dehydrogenases of the pentose phosphate pathway and transketolase in transplanted mouse hepatomas with different growth rates and in organs of tumor carriers].

The activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and transketolase were studied in the cytoplasmic fractions of transplanted mouse hepatomas differing in their growth rates, and in the liver, spleen and cortical layer of kidneys of tumour carriers and normal mice. It was shown that transplantation of hepatomas changes the activity of the pentose phosphate pathway enzymes in tumour carrier tissues unaffected by neoplasm. Deviations from normalcy were mainly similar to those observed in the hepatomas. The changes in the enzymatic activities were especially well-pronounced in the mice having rapidly growing hepatomas. This may be due to a generalized effect of the tumour on the organism, which is concurrent with malignancy.

Animals↗
PubMed1976

[Soluble, nuclear and mitochondrial forms of dehydrogenases, pentose-phosphate pathway transferases and nucleases in chicken liver].

The sub-cellular topography of oxidative and non-oxidative enzymes of the pentose phosphate pathway of carbohydrates metabolism and enzymes of the nucleic exchange (acid and alkaline deoxyribonucleases and ribonucleases) in chicken liver is studied. Nuclear and mitochondrial forms of the enzymes are discovered. The activity of the enzymes studied of carbohydrates metabolism is shown to correlate with that of the enzymes of nucleic metabolism in cytosol, nucleic and mitochondrial liver fractions.

Animals↗
PubMed1982

Histochemical studies of epithelial mucosubstances, respiratory and pentose shunt enzymes in the skin epidermis of the air-breathing fish Mastacembelus erythrotaenia (Mastacembelidae, Pisces).

The skin epidermis of the teleost fish Mastacembelus erythrotaenia has been studied by histochemical methods. 4 cell types were considered in the comparison; mucous goblet cells, sacciform cells, eosinophilic granular cells, and Malpighian cells. Succinate, isocitrate, glucose-6-phosphate, malate, and alpha-glycero-phosphate dehydrogenase did not indicate any changes in activity in the outer epidermal cell layers in comparison with the lower ones where the weakening or absence of the reactions could be inferred to a reversible metabolic state in the fields of the tricarboxylic acid cycle and pentose phosphate pathways. The strong activities of the above oxido-reductive enzymes found in the basal layer were correlated with the proliferative activity of stem cell differentiation and kinetic processes of cell division. The major component of the mucus produced by the mucous goblet cells consists of weakly acidic mucins showing in their carbohydrate moieties both the sialic acids and sulphated components with a lower degree of sulphation as evidenced by the appropriate histochemical methods. The sacciform cells produce a tryptophan rich protein and serotonin, the latter presumably acting in the control of mucus release since the N-acetylneuraminic acid is known to be an integral part of the serotonin receptor (Gottschalk 1972). Other functions related to the above amine may include its toxicity against the potential predators.

Alkaline Phosphatase↗
PubMed1982

Norepinephrine stimulation of pentose cycle in rat brain prisms.

Using the C1/C6 14CO2 ratio as a relative measure of pentose shunt metabolism, rat brain prisms were incubated with (1-14C) or (6-14C) glucose and respired 14CO2 collected. Shunt metabolism was stimulated with 10-4M but not 10-5M norepinephrine. MAO inhibitors and reserpine blocked norepinephrine stimulation but uptake inhibition did not. These data demonstrate that, under the tested conditions, MAO mediated norepinephrine metabolism does stimulate shunt activity but not at physiological concentrations.

Animals↗
PubMedDate not supplied

[Effect of sodium hydroxybutyrate on mitochondrial oxidative phosphorylation and myocardial pentose cycle enzymes during high altitude hypoxia].

The effect of intraperitoneal administration of sodium hydroxybutyrate on oxidative phosphorylation in mitochondria and on the activity of glucoso-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in the cardiac muscle was studied under alpine conditions (3200 m above the sea level). The drug was shown to increase the conjugation of oxidation with phosphorylation, to potentiate the activity of the test enzymes of the pentose cycle in the heart of the animals with one-month long adaptation to high-altitude hypoxia.

Acclimatization↗
PubMedDate not supplied

[Activity of enzymes of the oxidative part of the pentose phosphate pathway in skeletal muscles during muscular activity of different types and during the recovery period].

The activities of the enzymes of oxidative part of the pentose phosphate pathway - glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (EC 1.1.1.44) are studied in skeletal muscles of albino rats during muscular activity of different character and in the recovery period. The most essential decrease in the activity of dehydrogenases (glucose-6-phosphate dehydrogenase-by 33 and 6-phosphogluconate dehydrogenase - by 20%) is marked under the most intensive loading -4 min swimming with a load equal 12% of the animal body weight. On the contrary, in the recovery period after the muscular activity (15 min swimming) an increase is observed in the activity of these enzymes, especially in the late periods of the recovery (3 hours after rest).

Animals↗
PubMed1975

Histochemical observations on the occurrence of glycolytic and pentose phosphate cycle enzymes in the hepatopancreas and their possible relation to eyestalk factor(s) in the crab Scylla serrata (Forskal).

Histochemical studies were carried out on some of the glycolytic enzymes viz. phosphorylase, aldose, alpha-glycerophosphate dehydrogenase (alpha-GPDH) and lactic dehydrogenase (LDH) and a key enzyme of the pentose phosphatase cycle, glucose-6-phosphate dehydrogenase (G-6-PDH), in the hepatopancreas of Scylla serrata (Forskal). 1. Weak activities of phosphorylase and aldolase and strong-activities of alpha-GPDH and LDH were noticed mainly in the brush border of the tubules and R-cell cytoplasm. A trace activity of G-6-PDH was noticed in the brush border. 2. Bilateral eyestalk removal results in inhibition of both phosphorylase and aldolase. However, enhanced activities of alpha-GPDH and LDH were noticeable 4 h after the operation. The G-6-PDH activity remained unaltered till 24 h. 3. Injection of eyestalk extract into both intact and destalked crabs activated all the enzymes.

Animals↗
PubMedDate not supplied

[Activity of enzymes of tricarboxylic and pentose-phosphate cycles in dog brain with myocardial infarction].

Under conditions of experimental myocardium infarction caused in dogs by ligation of the anterior descending branch of the left coronary artery, the activity of alpha-ketoglutarate dehydrogenase and succinate dehydrogenase in mitochondria of the cortex, cerebellum and medulla ablongata lowers most intensively on the first and fifth day after the appearance of acute myocardium infarction. Activation of the most important enzymes of the pentose-phosphate cycle (glucose-6-phosphate dehydrogenase and transketolase) which is clearly pronounced on the fifth day is observed in the mentioned sections. In the authors' opinions the above changes in the activity of the enzymes are due to the brain hypoxia which may be the main reason of disturbance in the function of the central nervous system under this disease.

Animals↗
PubMedDate not supplied

[Characteristics of the pentose phosphate pathway of carbohydrate metabolism in the gastric mucosa of persons with peptic ulcer].

Activity of the main enzymes of pentose phosphate pathway of carbohydrate metabolism was studied in human mucosa of the stomach. In the mucosa glucose-6-phosphate dehydrogenase in gastric ulcer and 6-phosphogluconate dehydrogenase in normal stomach were shown to be less active as compared with these enzymatic activities in duodenal ulcer. A distinct decrease in the activity of glucose-6-phosphate dehydrogenase was observed in the ulcerous region, independently of the ulcer localization either in corpus ventriculi or in duodenum, as compared with the parts of the mucosa away from the impairment; the lowest enzymatic activity was estimated in the gastric ulcer zone. Activities of 6-phosphogluconate dehydrogenase and transketolase were the same in the ulcerous and normal mucosa and did not depend on the localization of the impairment. Contents of lactic and pyruvic acids were similar in mucosa of the stomach both in gastric and duodenal ulcer.

Duodenal Ulcer↗