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PubMed2004

Nucleic acid is a novel ligand for innate, immune pattern recognition collectins surfactant proteins A and D and mannose-binding lectin.

Collectins are a family of innate immune proteins that contain fibrillar collagen-like regions and globular carbohydrate recognition domains (CRDs). The CRDs of these proteins recognize various microbial surface-specific carbohydrate patterns, particularly hexoses. We hypothesized that collectins, such as pulmonary surfactant proteins (SPs) SP-A and SP-D and serum protein mannose-binding lectin, could recognize nucleic acids, pentose-based anionic phosphate polymers. Here we show that collectins bind DNA from a variety of origins, including bacteria, mice, and synthetic oligonucleotides. Pentoses, such as arabinose, ribose, and deoxyribose, inhibit the interaction between SP-D and mannan, one of the well-studied hexose ligands for SP-D, and biologically relevant d-forms of the pentoses are better competitors than the l-forms. In addition, DNA and RNA polymer-related compounds, such as nucleotide diphosphates and triphosphates, also inhibit the carbohydrate binding ability of SP-D, or approximately 60 kDa trimeric recombinant fragments of SP-D that are composed of the alpha-helical coiled-coil neck region and three CRDs (SP-D(n/CRD)) or SP-D(n/CRD) with eight GXY repeats (SPD(GXY)(8)(n/CRD)). Direct binding and competition studies suggest that collectins bind nucleic acid via their CRDs as well as by their collagen-like regions, and that SP-D binds DNA more effectively than do SP-A and mannose-binding lectin at physiological salt conditions. Furthermore, the SP-D(GXY)(8)(n/CRD) fragments co-localize with DNA, and the protein competes the interaction between propidium iodide, a DNA-binding dye, and apoptotic cells. In conclusion, we show that collectins are a new class of proteins that bind free DNA and the DNA present on apoptotic cells by both their globular CRDs and collagen-like regions. Collectins may therefore play an important role in decreasing the inflammation caused by DNA in lungs and other tissues.

Animals↗
PubMed1992

Nutritional value of D-xylose and L-arabinose for broiler chicks.

1. Two experiments were conducted to examine the effect of feeding D-xylose and L-arabinose on broiler performance, body composition, caecal length and weight, and liver weight. 2. Graded amounts (25, 50 and 75 g/kg) of D-xylose or L-arabinose were added to either a practical type (Exp. A) or a semi-purified (Exp. B) basal diet. As reference, a diet containing 75 g D-glucose/kg was included in both experiments, which were conducted in battery brooders, the birds receiving the isocaloric [on metabolisable energy (ME) basis] diets as dry mash ad libitum from 6 to 27 d of age. 3. A negative dose-dependent effect of both pentose sugars on weight gain and feed utilisation was observed. The same was true for daily food intake of the D-xylose diets. Water intake increased linearly (P less than 0.05) as the dietary concentrations of both pentose sugars was increased. Consequently, dry matter content of the droppings decreased. 4. Fat content of the chick body tended to decrease when either D-xylose or L-arabinose was included in the diets. 5. Caecal weight was increased markedly by feeding L-arabinose. Liver weight was not affected by feeding either D-xylose or L-arabinose to birds. 6. From data for ME intake and gain in body energy it was estimated that utilisation of the ME of both pentose sugars was inferior to that of D-glucose.

Animal Feed↗
PubMed1980

Relationship of malic enzyme activity to fatty acid synthesis and the pathways of glucose catabolism in developing rat liver.

The rates of fatty acid synthesis and the activity of several enzymes involved in lipid and carbohydrate metabolism were determined in livers from fetal, suckling, weanling and maternal rats. An estimate of the proportion of glucose catabolized via the pentose phosphate cycle and the Embden-Meyerhoff pathway was made using 14C- and 3H-labeled glucose. The contribution of pentose phosphate cycle-generated reducing equivalents to fatty acid synthesis was assessed using glucose-3-3H. Developmental changes in the activity of hepatic malic enzyme were not related to developmental changes in the rate of fatty acid synthesis as might be expected if this enzyme functioned to provide NADPH for fatty acid synthesis. Malic enzyme activity did not correlate with pentose phosphate cycle activity or with utilization for fatty acid synthesis of NADPH generated via this pathway.

Acetates↗
PubMed1998

Fructose-1,6-bisphosphate preserves adenosine triphosphate but not intracellular pH during hypoxia in respiring neonatal rat brain slices.

BACKGROUND: Fructose-1,6-bisphosphate (FBP) sometimes provides substantial cerebral protection during hypoxia or ischemia. 31P/1H nuclear magnetic resonance spectroscopy of cerebrocortical slices was used to study the effects of FBP on hypoxia-induced metabolic changes. In addition, 13C-labeled glucose was administered and 13C nuclear magnetic resonance spectroscopy was used to search for FBP-induced modulations in glycolysis and the pentose-phosphate pathway. METHODS: In each experiment, 80 slices (350 microm) obtained from ten 7-day-old Sprague-Dawley rat litter mates were placed together in a 20-mm nuclear magnetic resonance tube, perfused, and subjected to 30 min of hypoxia (PO2 < 3 mmHg). Nine experiments were performed, with n = 3 in each of three groups: (1) no treatment with FBP; (2) 60 min of prehypoxia treatment with FBP (2 mM); and (3) 60 min of posthypoxia treatment with FBP (2 mM). 31P/1H Interleaved nuclear magnetic resonance spectra at 4.7 T provided average adenosine triphosphate, intracellular pH, and lactate. Cresyl violet stains of random slices taken at predetermined time points were studied histologically. Some experiments had [2-13C]glucose in the perfusate. Slices from these studies were frozen for perchloric acid extraction of intracellular metabolites and studied with high-resolution 13C nuclear magnetic resonance spectroscopy at 11.75 T. RESULTS: With no pretreatment with FBP, hypoxia caused an approximately 50% loss of adenosine triphosphate, an approximately 700% increase in lactate, and a decrease in intracellular pH to approximately 6.4. Pretreatment with FBP resulted in no detectable loss of adenosine triphosphate, no increase in lactate, and minimal morphologic changes but did not alter decreases in intracellular pH. 13C Nuclear magnetic resonance spectra of extracted metabolites showed that pretreatment caused accumulation of [1-13C]fructose-6-phosphate, an early pentose-phosphate pathway metabolite. Posthypoxic treatment with FBP had no effects compared with no treatment. CONCLUSIONS: During severe hypoxia, pretreatment with FBP completely preserves adenosine triphosphate and almost completely preserves cell morphology but does not alter hypoxia-induced decreases in intracellular pH. Pretreatment also substantially augments the flux of glucose into the pentose-phosphate pathway.

Adenosine Triphosphate↗
PubMed1995

Oxidation of Imported or Endogenous Carbohydrates by Isolated Chloroplasts from Green Pepper Fruits.

Recently, we demonstrated that intact chloroplasts isolated from green pepper (Capsicum annum L.) fruits use exogenous glucose-6-phosphate (Glc-6-P) as the most efficient precursor for starch biosynthesis (O. Batz, R. Scheibe, H.E. Neuhaus [1995] Planta 196: 50-57). Here we demonstrate that these chloroplasts transport this hexose phosphate in counter-exchange for orthophosphate. By measuring the release of 14CO2 from [1-14C]Glc-6-P, we show that isolated fruit chloroplasts also use exogenous Glc-6-P as a substrate for the oxidative pentose-phosphate pathway. The rate of decarboxylation appears to be linear with time and is significantly reduced in the presence of Triton X-100, indicating that the reaction is dependent on plastid integrity. Pyruvate has been identified as a positive effector for flux through the oxidative pentose-phosphate pathway. However, the highest rates of Glc-6-P-driven oxidative pentosephosphate pathway activity are achieved in the presence of nitrite, 2-oxoglutarate, and glutamine, indicating a strong interaction between nitrogen metabolism and this pathway. In addition, we show that carbohydrates liberated during starch mobilization are used as substrates for the oxidative pentose-phosphate pathway. Orthophosphate was found to act as an activator for the observed 14CO2 release from carbohydrates formerly bound as starch. In this context, we demonstrate that exogenous Glc-6-P competes with endogenous carbohydrates. A possible interaction between exogenous and endogenous carbohydrates is discussed with respect to altered levels of carbohydrates during fruit development.

Journal Article↗
PubMed1969

Level of photosynthetic intermediates in isolated spinach chloroplasts.

The level of intermediates of the photosynthetic carbon cycle was measured in intact spinach chloroplasts in an attempt to determine the cause of the induction lag in CO(2) assimilation. In addition, transient changes in the level of the intermediates were determined as affected by a light-dark period and by the addition of an excess amount of bicarbonate during a period of steady photosynthesis. Assayed enzymically were: ribulose 1,5-diphosphate, pentose monophosphates (mixture of ribose 5-phosphate, ribulose 5-phosphate and xylulose 5-phosphate, hexose monophosphates (mixture of glucose 6-phosphate, glucose 1-phosphate, and fructose 6-phosphate), glyceraldehyde 3-phosphate, dihydroxyacetone phosphate, glycerate acid 3-phosphate, a mixture of fructose 1,6-diphosphate and sedoheptulose 1,7-diphosphate, adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP).The lag in CO(2) fixation appeared to be the result of low levels of pentose monophosphates. The level of ribulose 1,5-diphosphate was roughly equal in chloroplasts showing immediate linear kinetics with respect to CO(2) fixation and chloroplasts which exhibited an initial lag.Following a light-dark transition, CO(2) fixation ceased immediately but the level of glycerate 3-phosphate increased while ribulose 1,5-diphosphate was only slightly effected. The increase in level of glycerate 3-phosphate was correlated with a decrease in triose phosphate. Within 3 to 5 min in the light, ATP reached a maximum concentration while in darkness, all was utilized in 30 to 60 sec. The rapid loss of ATP was ascribed to an ATPase rather than to its utilization in kinase reactions.A rapid increase in CO(2) concentration enhanced the level of triose phosphate, but the level of glycerate 3-phosphate showed only a small overshoot and was considered as evidence that reducing power was not a rate limiting factor. Data were obtained indicating that triose phosphates similar to pentose monophosphates and in contrast to fructose 6-phosphate, glucose 6-phosphate and glucose 1-phosphate could be transported between chloroplast and suspending medium. Differential import and export of phosphorylated compounds may serve as routes alternative to starch and sucrose for the flow of carbon into biosynthetic pathways.

Journal Article↗
PubMed1970

P(700) activity and chlorophyll content of plants with different photosynthetic carbon dioxide fixation cycles.

Representative plants containing either the reductive pentose phosphate cycle or the C(4) dicarboxylic acid cycle of photosynthetic carbon dioxide fixation have distinctly different contents of P(700) and chlorophylls a and b. With leaf extracts and isolated chloroplasts from C(4) cycle plants, the mean value of the relative ratio of P(700) to total chlorophyll was 1.83 and the mean value of the ratio of chlorophyll a to b was 3.89. The respective values in similar extracts and chloroplasts from pentose cycle plants are 1.2 and 2.78.It seems likely that these results are indicative of a more active Photosystem I or a different size photosynthetic unit in C(4) cycle plants than in the reductve pentose phosphate cycle plants.

Journal Article↗
PubMed1974

Transition of metabolisms in living popular bark from growing to wintering stages and vice versa: changes in glucose 6-phosphate and 6-phosphogluconate dehydrogenase activities and in the levels of sugar phosphates.

Activities of glucose 6-phosphate, 6-phosphogluconate, and isocitrate dehydrogenases, together with intermediate levels of the glycolytic pathway and the pentose phosphate cycle, were measured throughout a year in the living bark of poplar (Populus gelrica). Shoots, immediately after budding (early May), contained very high levels of the three enzyme activities, which fell gradually by early or mid-July to a level, roughly equivalent to budding (May) or growing (July) 2-year-old twigs. In September, the former two dehydrogenase activities of the new shoots and 2-year-old twigs began to rise, while the latter activity started to decrease. The rise of the two dehydrogenase activities continued until late November (or early December). The high level of the two dehydrogenase activities lasted until early in April of the following year and then the decrease in the activities began prior to the onset of budding, reaching a low, basal level in early May. The profile of changes in the two dehydrogenase activities appeared to coincide with the increase and decrease of soluble proteins.Normal concentrations of total hexose phosphates in the glycolytic pathway plus 6-phosphogluconate were found to be 288 to 895 mumoles/kilogram dry weight. During the metabolism transition (September and April), a transient and striking increase of 6-phosphogluconate was observed. In September, 6-phosphogluconate reached a level on the order of 10(-4)m and was 4 times that of fructose 6-phosphate. The increase in 6-phosphogluconate coincided with the increase in the glucose 6-phosphate dehydrogenase activity. Coincidentally, with the change of 6-phosphogluconate level, a large deviation of the in vivo ratio of fructose 6-phosphate to glucose 6-phosphate from the known equilibrium constant was observed, showing the relation of pentose phosphate cycle enzyme activity to the control of glycolysis. The ratio of glucose 6-phosphate to glucose 1-phosphate deviated from that predicted. These ratios fluctuated throughout the year and were affected by the growth phases. The levels of pentose phosphate cycle metabolites, except for 6-phosphogluconate, in the bark were extremely low.The level of inorganic phosphate in the living bark throughout the year was dependent upon the growth phases, suggesting the presence of a regulatory mechanism to maintain inorganic phosphate at a given level as the growth phase changed.Sugar phosphate levels of popular twigs or potato tubers (Solanum tuberosum) remained constant after they were stored for 2 weeks at low temperatures, whereas in sweet potato roots (Ipomoea batatas), the level rose to about 9-fold of the control, indicating the presence of a strict regulatory system for the synthesis and catabolism of sugar phosphate in the former two.

Journal Article↗
PubMed1979

Salt Requirement for Crassulacean Acid Metabolism in the Annual Succulent, Mesembryanthemum crystallinum.

In experiments with the facultative Crassulacean acid metabolism (CAM) species, Mesembryanthemum crystallinum, only plants which received high levels of inorganic salts fixed substantial amounts of CO(2) by the CAM pathway. Equivalent osmolarities of polyethylene glycol 6000 did not yield any CAM fixation. Plant water potential and turgor pressure had no detectable influence on the amount of CAM fixation. These observations rule out the possibility that the inorganic ions were acting as osmotic agents.Carbon dioxide and water exchange analysis showed that when water supply was not limiting, salt-deprived plants sustained higher reductive pentose phosphate cycle carbon fixation rates than salt-treated plants. Under water stress conditions, salt-deprived plants using only the reductive pentose phosphate cycle pathway assimilated less carbon and were less efficient in their water use than salt-treated plants using predominately the CAM pathway. These results support the hypothesis that the ability to use the CAM pathway reduces the capacity for reductive pentose phosphate cycle fixation but permits higher productivity in water-limited environments.

Journal Article↗
PubMed1989

Developmental Control of Apiogalacturonan Biosynthesis and UDP-Apiose Production in a Duckweed.

Vegetative fronds of Spirodela polyrrhiza were induced to form dormant turions by the addition of 1 micromolar abscisic acid or by shading. The cell wall polymers of fronds contained a high proportion of the branched-chain pentose, d-apiose (about 20% of total noncellulosic wall sugar residues), whereas turion cell walls contained only trace amounts (about 0.2%). When the fronds were fed d-[(3)H]glucuronic acid for 30 minutes, the accumulated UDP-[(3)H]apiose pool accounted for about 27% of the total phosphorylated [(3)H]pentose derivatives; in turions, the UDP-[(3)H]apiose pool accounted for only about 4% of the total phosphorylated [(3)H]pentose derivatives. We conclude that the developmentally regulated decrease in the biosynthesis of a wall polysaccharide during turion formation involves a reduction in the supply of the relevant sugar nucleotide. One controlling enzyme activity is suggested to be UDP-apiose/UDP-xylose synthase. However, since there was a 100-fold decrease in the rate of polysaccharide synthesis and only a 9-fold decrease in UDP-apiose accumulation, there is probably also control of the activity of the relevant polysaccharide synthase.

Journal Article↗
PubMed1982

Epididymal carbohydrate metabolism in experimental hypercorticosteronism: studies on mature male rats.

Corticosterone induced changes in serum hormonal profiles and the key enzymes involved in glycolytic and pentose phosphate pathways were studied in caput, corpus and cauda epididymides of mature male rate (200-250 g body weight). Corticosterone (3.5 mg/100 g body weight sc. for 20 days) treatment was found to depress serum testosterone and prolactin while the gonadotrophins were unaltered. Enzymes of both the glycolytic and pentose phosphate pathways were significantly decreased in caput epididymidis. But in corpus and cauda epididymides only the glycolytic enzymes were reduced. Withdrawal of treatment (for 20 days), resulted in restoration of the glycolytic enzymes to normalcy. Tge serum hormonal profiles were also found to be within the normal range. The pentose phosphate pathway in caput epididymidis showed a significant increase in enzyme activities following withdrawal of treatment. From the present investigation it is clear that hypercorticosteronism had a definite influence on epididymal enzymes involved in carbohydrate metabolism.

Animals↗
PubMed2004

The crystal structure of glucose-6-phosphate isomerase from Leishmania mexicana reveals novel active site features.

Glucose-6-phosphate isomerase catalyzes the reversible aldose-ketose isomerization of D-glucose-6-phosphate to D-fructose-6-phosphate in glycolysis and gluconeogenesis, and in the recycling of hexose-6-phosphate in the pentose phosphate pathway. The unicellular protozoans, Trypanosoma brucei, T. cruzi and Leishmania spp., of the order Kinetoplastida are important human parasites responsible for African sleeping sickness, Chagas' disease and leishmaniases, respectively. In these parasites, glycolysis is an important (and in some cases the only) metabolic pathway for ATP supply. The first seven of the 10 enzymes that participate in glycolysis, as well as an important fraction of the enzymes of the pentose phosphate pathway, are compartmentalized in peroxisome-like organelles called glycosomes. The dependence of the parasites on glycolysis, the importance of the pentose phosphate pathway in defense against oxidative stress, and the unique compartmentalization of these pathways, point to the enzymes contained in the glycosome as potential targets for drug design. The present report describes the first crystallographic structure of a parasite (Leishmania mexicana) glucose-6-phosphate isomerase. A comparison of the atomic structure of L. mexicana, human and other mammalian PGIs, which highlights unique features of the parasite's enzyme, is presented.

Amino Acid Sequence↗
PubMedDate not supplied

Effect of adrenalectomy and corticosterone replacement on epididymal carbohydrate metabolism--studies on mature male rats.

The effect of adrenalectomy and corticosterone replacement on epididymal enzymes involved in obligatory steps of glycolysis and pentose phosphate pathway were studied along with serum hormonal profiles. Adrenalectomy was found to elevate serum prolactin while the gonadotropins and testosterone were unaltered. In caput epididymal tissue enzymes of the pentose phosphate pathway. Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities were increased after adrenalectomy. However, in corpus epididymal tissue the key enzymes viz. hexokinase, 6-phosphofructokinase and pyruvatekinase of the glycolytic pathway were elevated leaving the pentose phosphate pathway unaffected. Adrenalectomy was also found to favour glycolysis of the epididymal spermatozoa. The possible direct effect of prolactin is discussed to explain the enzymatic changes in epididymis. Corticosterone replacement was found to maintain the enzyme activities along with serum prolactin and corticosterone at control levels. In conclusion, it is suggested that the adrenalectomy induced changes in enzyme activities could be due to the direct effect of prolactin.

Adrenalectomy↗
PubMed1976

Influence of growth temperature on glucose metabolism of a psychotrophic strain of Bacillus cereus.

The influence of temperature on glucose metabolism of a psychotrophic strain of Bacillus cereus was investigated. The pH of the growth medium and spore-forming frequencies of B. cereus varied when grown at 32, 20, or 7 C. Radiorespirometric analyses revealed that vegetative cells of B. cereus metabolized glucose by simultaneous operation of the Embden-Meyerhof-Parnas pathway and the pentose phosphate pathway. As the growth temperature decreased, glucose was metabolized with increased participation of the pentose phosphate pathway. The shift of cells grown at a higher temperature to a lower temperature increased the relative participation of the pentose phosphate pathway, whereas the shift of cells grown at low temperatures to a higher temperature had the opposite effect. Cells of late logarithmic phase grown at 20 and 7 C oxidized acetate by the tricarboxylic acid cycle reaction. However, cells grown at 32 C failed to oxidize acetate to CO2 to any appreciable extent. The extracellular products resulting from the metabolism of glucose decreased as the growth temperature was lowered. Organic acids were the major extracellular products of cultures grown at 32 and 20 C. Acetic acid, lactic acid, and pyruvic acid together accounted for 86.1 and 78.9% of extracellular radioactivity, respectively, at the two temperatures. The relative ratio of these three acids varied between the temperatures. Little or no acid accumulated at 7 C.

Acetates↗
PubMed1979

Xylose, arabinose, and rhamnose fermentation by Bacteroides ruminicola.

Metabolism and growth yields of Bacteroides ruminicola grown on d-xylose, l-arabinose, and l-rhamnose were studied. Growth yields were 62, 68, and 35.5 g (dry weight) per mol of carbohydrate fermented after correction for storage polysaccharide. Experiments with [1-(14)C]arabinose indicated that pentose was fermented by a pentose phosphate cycle plus glycolysis, with some indication of a minor phosphoketolase-type pathway. The product ratios from pentose were similar to those previously described for hexose. Rhamnose was fermented mainly to 1,2-propanediol, succinate, and acetate, although the latter was quantitatively less than expected. Estimates of adenosine 5'-triphosphate (ATP) molar growth yields could not be calculated with any certainty, as ATP generation by electron transport-linked phosphorylation cannot yet be assessed. If ATP were generated by substrate-level phosphorylation reactions alone, ATP molar growth yields for xylose, arabinose, and rhamnose would be 30, 28, and 35 g/mol. If calculations are based on an assumption that two ATP are generated by electron transport-linked phosphorylation per succinate, ATP molar growth yields become 15, 14, and 22 g/mol; if the assumption is also made that the pathway of lactaldehyde reduction is coupled to production of one ATP per 1,2-propanediol by electron transport-linked phosphorylation, the ATP molar growth yield for rhamnose fermentation becomes 14 g/mol. No preference can be expressed between these alternatives at present.

Adenosine Triphosphate↗
PubMed1985

Glucose catabolism in strains of acidophilic, heterotrophic bacteria.

Pathways of glucose catabolism, potentially operational in six strains of obligately aerobic, acidophilic bacteria, including Acidiphilium cryptum strain Lhet2, were investigated by short-term radiorespirometry and enzyme assays. Short-term radiorespirometry was conducted at pH 3.0 with specifically labeled [C]glucose. The high rate and yield of C-1 oxidized to CO(2) indicated that the Entner-Doudoroff, pentose phosphate, or both pathways were operational in all strains. Apparent nonequivalent yields of CO(2) from C-1 and estimated CO(2) from C-4 (C-1 > C-4) were suggestive of simultaneous glucose catabolism by both pathways in all strains tested. Variation in the relative contribution of the two pathways of glucose catabolism appears to account for observed strain differences. Calculation of the actual percent pathway participation was not feasible. Enzyme assays were completed with crude extracts of glucose-grown cells to substantiate the results obtained by radiorespirometry. The key enzymes of the pentose phosphate pathway (6-phosphogluconate dehydrogenase) and the Entner-Doudoroff pathway (2-keto-3-deoxy-6-phosphogluconate aldolase and 6-phosphogluconate dehydrase) were present in all strains examined (PW2, Lhet2, KLB, OP, and QBP). However, none of the strains exhibited detectable levels of the key enzyme of the Embden-Meyerhof-Parnas pathway, 6-phosphofructokinase. All strains contained glucose-6-phosphate dehydrogenase and fructose bisphosphate aldolase. The results of the enzyme study supported the contention that the pentose phosphate and Entner-Doudoroff pathways are operational for glucose catabolism in the acidophilic heterotrophs, and that the Embden-Meyerhof-Parnas pathway is apparently absent.

Journal Article↗
PubMed2003

A modified Saccharomyces cerevisiae strain that consumes L-Arabinose and produces ethanol.

Metabolic engineering is a powerful method to improve, redirect, or generate new metabolic reactions or whole pathways in microorganisms. Here we describe the engineering of a Saccharomyces cerevisiae strain able to utilize the pentose sugar L-arabinose for growth and to ferment it to ethanol. Expanding the substrate fermentation range of S. cerevisiae to include pentoses is important for the utilization of this yeast in economically feasible biomass-to-ethanol fermentation processes. After overexpression of a bacterial L-arabinose utilization pathway consisting of Bacillus subtilis AraA and Escherichia coli AraB and AraD and simultaneous overexpression of the L-arabinose-transporting yeast galactose permease, we were able to select an L-arabinose-utilizing yeast strain by sequential transfer in L-arabinose media. Molecular analysis of this strain, including DNA microarrays, revealed that the crucial prerequisite for efficient utilization of L-arabinose is a lowered activity of L-ribulokinase. Moreover, high L-arabinose uptake rates and enhanced transaldolase activities favor utilization of L-arabinose. With a doubling time of about 7.9 h in a medium with L-arabinose as the sole carbon source, an ethanol production rate of 0.06 to 0.08 g of ethanol per g (dry weight). h(-1) under oxygen-limiting conditions, and high ethanol yields, this yeast strain should be useful for efficient fermentation of hexoses and pentoses in cellulosic biomass hydrolysates.

Arabinose↗
PubMed1974

Glucose metabolism in Neisseria gonorrhoeae.

The metabolism of glucose was examined in several clinical isolates of Neisseria gonorrhoeae. Radiorespirometric studies revealed that growing cells metabolized glucose by a combination on the Entner-Doudoroff and pentose phosphate pathways. A portion of the glyceraldehyde-3-phosphate formed via the Entner-Doudoroff pathway was recycled by conversion to glucose-6-phosphate. Subsequent catabolism of this glucose-6-phosphate by either the Entner-Doudoroff or pentose phosphate pathways yielded CO(2) from the original C6 of glucose. Enzyme analyses confirmed the presence of all enzymes of the Entner-Doudoroff, pentose phosphate, and Embden-Meyerhof-Parnas pathways. There was always a high specific activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) relative to that of 6-phosphogluconate dehydrogenase (EC 1.1.1.44). The glucose-6-phosphate dehydrogenase utilized either nicotinamide adenine dinucleotide phosphate or nicotinamide adenine dinucleotide as electron acceptor. Acetate was the only detectable nongaseous end product of glucose metabolism. Following the disappearance of glucose, acetate was metabolized by the tricarboxylic acid cycle as evidenced by the preferential oxidation of [1-(14)C]acetate over that of [2-(14)C]acetate. When an aerobically grown log-phase culture was subjected to anaerobic conditions, lactate and acetate were formed from glucose. Radiorespirometric studies showed that under these conditions, glucose was dissimilated entirely by the Entner-Doudoroff pathway. Further studies determined that this anaerobic dissimilation of glucose was not growth dependent.

Acetates↗