Pathways of glucose catabolism during germination of Streptomyces spores

Abstract The participation of the different glucose-catabolic pathways during germination of Streptomyces antibioticus spores was studied. In dormant spores, glucose is catabolized through the pentose phosphate (PP) and the Embden-Meyerhof-Parnas (EMP) pathways, with an active tricarboxylic acid cycle. The relative participation of each catabolic pathway is regulated by germinative or non-germinative conditions. During spore germination, the pentose phosphate pathway continuously increased in its participation in the glucose catabolism and it was the major glucose-catabolic pathway in the exponential phase of growth. In addition, it showed the existence of an active tricarboxylic acid cycle in dormant spores, which was being drained for biosynthetic purposes.     

Glucose Catabolism of Erysipelothrix rhusiopathiae

The pathways of glucose catabolism in Erysipelothrix rhusiopathiae have been identified by the radiorespirometric technique. The radiorespirometric data showed that 96% of the glucose catabolism was via the Embden-Meyerhof-Parnas pathway with the remaining 4% dissimilated by the hexose monophosphate pathway. The products of the anaerobic dissimilation of glucose were determined. Lactic acid was the major product; ethyl alcohol, acetic acid, formic acid, and carbon dioxide were formed in smaller amounts.     

Carbohydrate Catabolism in Azospirillum amazonense

The nitrogen fixer Azospirillum amazonense grew on the various disaccharides, hexoses, and pentoses tested in this study but not on polyols and on some tricarboxylic acid cycle intermediates. An active transport system was detected for sucrose and glucose but not for mannitol and 2-ketoglutarate. Six A. amazonense strains were examined for 16 carbon-metabolizing enzymes, and the results indicate that these strains employ the Entner-Doudoroff pathway to catabolize sucrose, fructose, and glucose. The hexose monophosphate and Embden-Meyerhof-Parnas pathways were not detectable.     

Catabolic pathways of glucose in Bacillus circulans var. alkalophilus

Enzymes and the metabolic pathways of glucose catabolism of Bacillus circulans var. alkalophilus were studied. The metabolism of the microbe was mixed acid fermentative yielding mainly acetic and formic acids as end products from glucose. It was estimated that B. circulans var. alkalophilus partitions 90%–93% of the carbon from glucose into the Embden-Meyerhof-Parnas (EMP) pathway and 7%–10% into the hexose monophosphate (HMP) and Entner-Doudoroff (ED) pathways. Rather low activities of glucose dehydrogenase and gluconokinase appeared in the early logarithmic and late stationary phases, whereas NADH oxidase was markedly high. This result can be explained by a demand to reduce NADH to NAD⁺ for the EMP pathway; when acetic and formic acids are produced, no NADH is regenerated to NAD⁺, which is required in the early steps of EMP and HMP pathways. A small percentage (1.6%–2.4%) of the total CO₂ was formed from (6-C) of glucose, which means that the tricarboxylic acid cycle was functional but its contribution was insignificant. Large differences do not seem to exist between alkaliphilic and neutrophilic bacilli in the use of glucose pathways. Received: January 29, 1999 / Accepted: July 30, 1999     

Glucose metabolism by trout (Salmo trutta) red blood cells

Summary Glucose metabolism has been studied in Salmo trutta red blood cells. From non-metabolizable analogue (3-O-methyl glucose and l-glucose) uptake experiments it is concluded that there is no counterpart to the membrane transport system for glucose found in mammalian red blood cells. Once within the cells, glucose is directed to CO₂ and lactate formation through both the Embden-Meyerhoff and hexose monophosphate shunts; lactate appears as the most important endproduct of glucose metabolism in these cells. From experiments under anaerobic conditions, and in the presence of an inhibitor of pyruvate transfer to mitochondria, most of the CO₂ formed appears to derive from the hexose monophosphate pathway. Appreciable O₂ consumption has been detected, but there is no clear relationship between this and substrate metabolism. Key enzymes of glucose metabolism hexokinase, fructose-6-phosphate kinase and, probably, pyruvate kinase are out of equilibrium, confirming their regulatory activity in Salmo trutta red blood cells. The presence of isoproterenol, a catecholamine analogue, induces important changes in glucose metabolism under both aerobic and anaerobic conditions, and increases the production of both CO₂ and lactate. From the data presented, glucose appears to be the major fuel for Salmo trutta red blood cells, showing a slightly different pattern of glucose metabolism from rainbow trout red blood cells.Abbreviations EM Embden-Meyerhoff pathway - G6D glucose-6-phosphate dehydrogenase - GOT glutamate oxalacetate transaminase - GPI glucose phosphate isomerase - HK hexokinase - HMS hexose monophosphate shunt - IP isoproterenol - LDH lactate dehydrogenase - MCB modified Cortland buffer - OMG 3-O-methyl glucose - PFK fructose-6-phosphate kinase - PK pyruvate kinase - RBC red blood cells - TAC tricarboxylic acid cycle     

Glucose catabolism in two derivatives of a Rhizobium japonicum strain differing in nitrogen-fixing efficiency.

Radiorespirometric and enzymatic analyses reveal that glucose-grown cells of Rhizobium japonicum isolates I-110 and L1-110, both derivatives of R. japonicum strain 3I1b110, possess an active tricarboxylic acid cycle and metabolize glucose by simultaneous operation of the Embden-Meyerhof-Parnas and Entner-Doudoroff pathways. The hexose cycle may play a minor role in the dissimilation of glucose. Failure to detect the nicotinamide adenine dinucleotide phosphate-dependent decarboxylating 6-phosphogluconate dehydrogenase (EC 1.1.1.44) evidences absence of the pentose phosphate pathway. Transketolase and transaldolase reactions, however, enable R. japonicum to produce the precursors for purine and pyrimidine biosynthesis from fructose-6-phosphate and glyceraldehyde-3-phosphate. A constitutive nicotinamide adenine dinucleotide-linked 6-phosphogluconate dehydrogenase has been detected. The enzyme is stimulated by either mannitol or fuctose and might initiate a new catabolic pathway. R. japonicum isolate I-110, characterized by shorter generation times on glucose and greater nitrogen-fixing efficiency, oxidizes glucose more extensively than type L1-110 and utilizes preferentially the Embden-Meyerhof-Parnas pathway, whereas the Entner-Doudoroff pathway apparently predominates in type L1-110.     

The obligatory involvement of the electron transport system in the catabolic metabolism ofHaemophilus parainfluenzae

Antonie van Leeuwenhoek - The catabolic metabolism ofHaemophilus parainfluenzae involves the activity of enzymes of the Embden-Meyerhof-Parnas pathway, the hexose monophosphate pathway, and the...     

Comparative studies on the glycolytic and hexose monophosphate pathways in Candida parapsilosis and Saccharomyces cerevisiae

Some enzymatic activities of the glycolytic and hexose monophosphate pathways of Candida parapsilosis, a yeast lacking alcohol dehydrogenase but able to grow on high glucose concentrations, were compared to those of Saccharomyces cerevisiae. Cells were grown either on 8% glucose or on 2% glycerol and activities measured under optimal conditions. Results were as follows: glycolytic enzymes of C. parapsilosis, except glyceraldehyde 3-phosphate dehydrogenase, exhibited an activity weaker than that of S. cerevisiae, especially when yeasts were grown on glycerol. Fructose-1,6 bisphosphatase, an enzyme implicated in gluconeogenesis and in the hexose monophosphate pathway, and known to be very sensitive to catabolite repression in S. cerevisiae, was always active in C. parapsilosis even when cells were grown on 8% glucose. However, the allosteric properties towards AMP and fructose-2,6-bisphosphate were the same in both strains. Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, two other enzymes of the hexose monophosphate pathway, exhibited a higher activity in C. parapsilosis than in S. cerevisiae. Regulation of two important control points of the glycolytic flux, phosphofructokinase and pyruvate kinase, was investigated. In C. parapsilosis phosphofructokinase was poorly sensitive to ATP but fructose-2,60bisphosphate completely relieved the light ATP inhibition. Pyruvate kinase did not require fructose-1,6-bisphosphate for its activity, and by this way, did not regulate the glycolytic flux. The high glyceraldehyde-3-P-dehydrogenase activity, together with the relative insensitivity of fructose-1,6-bisphosphatase to catabolite repression and the high glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities suggested that in C. parapsilosis, as in other Candida species and opposite to S. cerevisiae, the glucose degradation mainly occurred through the hexose monophosphate pathway, under both growth conditions used.Abbreviations C. parapsilosis Candida parapsilosis - S. cerevisiae Saccharomyces cerevisiae - C. utilis Candida utilis     

Glucose metabolism of thraustochytrium roseum,a nonfilamentous marine phycomycete

Summary In uniformly labeled logarithmic-phase cells of Thraustochytrium roseum grown in isotopic glucose, 85% of the respiratory CO₂ was derived from endogenous reserves and only 15% was contributed by exogenous glucose. Experiments with asymetrically labeled glucose showed that the main portion of metabolic CO₂ came from carbon 1 of the glucose molecule, suggesting that the hexose monophosphate shunt is a major pathway for glucose dissimilation in the fungus. The presence of several enzymes of the hexose monophosphate shunt, the Embden-Meyerhof and glyoxylate pathways, and the tricarboxylic acid cycle were demonstrated.     

Disturbed sugar metabolism in a fully habituated nonorganogenic callus of Beta vulgaris (L.)

Habituated (H) nonorganogenic sugarbeet callus was found to exhibit a disturbed sugar metabolism. In contrast to cells from normal (N) callus, H cells accumulate glucose and fructose and show an abnormal high fructose/glucose ratio. Moreover, H cells which have decreased wall components, display lower glycolytic enzyme activities (hexose phosphate isomerase and phosphofructokinase) which is compensated by higher activities of the enzymes of the hexose monophosphate pathway (glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase). The disturbed sugar metabolism of the H callus is discussed in relation to a deficiency in H₂O₂ detoxifying systems.Abbreviations 6PG-DH 6-phosphogluconate dehydrogenase - G6P-DH glucose-6-phosphate dehydrogenase - H fully habituated callus - HK hexokinase - HMP hexoses monophosphate - HPI hexose phosphate isomerase - N normal callus - PFK phosphofructokinase     

Role of carbon dioxide in germination of spores of Streptomyces viridochromogenes

CO₂ in required continuously during germination of Streptomyces viridochromogenes spores. Spores incubated in a defined germination medium in the absence of CO₂ remain phase bright and do not release spore carbon. In the presence of CO₂, the spores initiate germination accompanied by loss of refractility and spore carbon. The CO₂ requirement is replaced by oxaloacetate or a mixture of tricarboxylic acid cycle (TCA) intermediates. Labeled CO₂ is taken up by germinating spores, and is incorporated into protein and RNA. TCA cycle intermediates and related amino acids contain most of the acid-soluble label following short term exposures of germinating spores to ¹⁴CO₂. TCA cycle inhibitors repress germination and ¹⁴CO₂ uptake whereas folic acid antagonists do not. The results indicate that CO₂ is incorporated into oxaloacetate which is converted to biosynthetic intermediates required for germination. Operation of the TCA cycle appears to be essential for spore germination. The conclusion is reached that CO₂ is required during germination in order to maintain the cycle by an anaplerotic reaction.Abbreviations SN sucrose-nitrate medium - TX buffer Trisbuffer pH 7.3 containing-Triton X-100 - DGM defined germination medium - TX salts TX buffer plus Mg and Ca ions - TA trichloroacctic acid - TCA tricarboxylic acid     

Fructose catabolism in Azospirillum brasilense and Azospirillum lipoferum.

The pathways for catabolism of fructose were investigated in the type strains of Azospirillum lipoferum and Azospirillum brasilense grown aerobically with (NH4)2SO4 as the nitrogen source. When grown on fructose, the former species possessed a complete Entner-Doudoroff pathway, whereas the latter species lacked activity for glucose-6-phosphate dehydrogenase. Both species possessed a complete catabolic Embden-Meyerhof-Parnas pathway. Neither species possessed the key enzyme of the hexose monophosphate pathway, 6-phosphogluconate dehydrogenase. Both species could phosphorylate fructose to fructose-1-phosphate by means of a phosphoenolpyruvate-phosphotransferase system, and high activities of 1-phosphofructokinase occurred. Both species possessed glucokinase activity, but only A. lipoferum had hexokinase activity; moreover, the cells of A. brasilense were nearly impermeable to glucose, accounting for the inability of this species to grow on glucose. Both species possessed pyruvate dehydrogenase, a complete tricarboxylic acid cycle, a glyoxylate shunt, and malic enzyme. Analysis of the acidic end products for both species indicated the formation of only small amounts of various organic acids, and most of the titratable acidity was due to utilization of the ammonium ions of the medium. Gluconic acid was not formed during growth of either species on fructose but was detected during growth of A. lipoferum on glucose; this species also possessed an NADP-linked glucose dehydrogenase and gluconokinase.     

Hexose monophosphate pathway in synapses

Abstract— Synaptosomes isolated from rat cerebral cortex converted [l-¹⁴C]glucose more rapidly than [6-²⁴C]glucose to ^,14CO₂. The ratio of C-l: C-6 in ¹⁴CO₂ was 3-9, thus suggesting that the hexose monophosphate shunt (HMP) pathway was functional in synapses in vitro. When changes in the ratio of C-l: C-6 in ¹⁴CO₂ were used as an index of shunt activity, glucose oxidation by this route was stimulated by electron acceptors as well as by neurohormones, including norepinephrine, acetylcholine and serotonin. Brain mince also exhibited a C-l: C-6 ratio of 3-2 when short (15 min) incubations were employed. Negative results previously reported are attributable to prolonged incubation during which depletion of NADP or randomization of the labelled carbons in radioactive glucose could have occurred. Our experiments excluded the incorporation of glucose into macromolecules as a specific role for the hexose monophosphate pathway. The generation of NADPH for numerous metabolic reactions including the maintenance of membrane SH groups and the oxidation and hydroxylation reactions may represent the functions of the hexose monophosphate in synaptosomes and account for its stimulation by neurohormones.     

A study of the role of the hexose monophosphate pathway with respect to fatty acid biosynthesis in sporulation of Saccharomyces cerevisiae

13C NMR was used to study the pattern of label incorporation from [2-13C]acetate into trehalose during sporulation in Saccharomyces cerevisiae. A wild-type strain and a strain homozygous for the zwf1 mutation (which affects glucose-6-phosphate dehydrogenase) were used. In the wild-type it was possible to deduce the cycling of glucose 6-phosphate around the hexose monophosphate pathway whilst in the mutant strain this did not occur. The requirement of the hexose monophosphate pathway for providing NADPH for fatty acid biosynthesis was examined using 13C NMR and GC/MS. The wild-type strain produced a typical profile of fatty acids with palmitoleic acid being the most abundant whereas the mutant contained only one-quarter the amount of total fatty acid. As zwf1 homozygous diploids are able to sporulate this indicates that the large amount of fatty acid biosynthesis observed in sporulation of wild-type strains is not essential to the process.     

Comparative profiles of the hexose monophosphate dehydrogenases in rat tissues over the lactation cycle

The mammary gland tissue hexose monophosphate dehydrogenase activities were low in virgin, pregnant and weaned rats, but increased at the onset of lactation. The muscle and liver glucose 6-phosphate dehydrogenase activity peaked at early and late lactation respectively. The liver 6-phosphogluconate dehydrogenase peaked in late pregnancy and remained elevated through lactation. The muscle 6-phosphogluconate dehydrogenase peaked at the onset of lactation. The adipose tissue hexose monophosphate dehydrogenases exhibited small changes during pregnancy and lactation. The spleen hexose monophosphate dehydrogenases did not respond to lactation An overshoot in both the liver and the adipose tissue hexose monophosphate dehydrogenases was observed on weaning. Serum glucose levels remained unchanged throughout pregnancy, lactation and weaning. Only liver glucose 6-phosphate dehydrogenase activity correlated with plasma insulin, which also correlated positively with food consumption. The results demonstrate that tissue-specific control of the hexose monophosphate dehydrogenases occurs in the female rat during its complete lactation cycle.     

13C NMR studies of the fluxes in the central metabolism of Corynebacterium glutamicum during growth and overproduction of amino acids in batch cultures

The carbon flux distribution in the central metabolism of Corynebacterium glutamicum was studied in batch cultures using [1-¹³C]- and [6-¹³C]glucose as substrate during exponential growth as well as during overproduction of l-lysine and l-glutamate. Using the ¹³C NMR data in conjunction with stoichiometric metabolite balances, molar fluxes were quantified and normalised to the glucose uptake rate, which was set to 100. The normalised molar flux via the hexose monophosphate pathway was 40 during exponential growth, whereas it was only 17 during l-glutamate production. During l-lysine production, the normalised hexose monophosphate pathway flux was elevated to 47. Thus, the carbon flux via this pathway correlated with the NADPH demand for bacterial growth and l-lysine overproduction. The normalised molar flux in the tricarboxylic acid cycle at the level of 2-oxoglutarate dehydrogenase was 100 during exponential growth and 103 during l-lysine secretion. During l-glutamate formation, the normalised flux through the tricarboxylic acid cycle was reduced to 60. In contrast to earlier NMR studies with C. glutamicum, no significant activity of the glyoxylate pathway could be detected. All experiments indicated a strong in vivo flux from oxaloacetate back to phosphoenolpyruvate and/or pyruvate, which might be due to phosphoenolpyruvate carboxykinase activity in C. glutamicum.     

RESPIRATORY METABOLISM IN ACHLYA AMBISEXUALIS

Manometric and spectrophotometric techniques were utilized in studying respiratory metabolism in intact mycelia and cell-free extracts of the heterothallic water mold, Achlya ambisexualis Raper. Enzymes representing the hexose monophosphate pathway, the Embden-Meyerhof-Parnas scheme, the tricarboxylic acid (TCA) cycle and a terminal cytochrome system were demonstrated. In addition, glycerol phosphate dehydrogenase and lactic dehydrogenase activities were observed. Activities of selected enzymes were observed to decline with culture-age, with the exceptions of glucose-6-phosphate dehydrogenase and glycerol-phosphate dehydrogenase. Oxygen uptake in the male strain more than doubled in the presence of sexual hormone A.     

A novel pathway of glucose catabolism in Thiobacillus novellus

Phosphoketolase (E.C. 4.1.2.9) was found in crude extracts of Thiobacillus novellus (ATCC 8093) with a specific activity of 0.070 mol triose formed min^-1 (mg protein)^-1. The pH optimum, 6.0, temperature optimum, 43° C, and K _m , 4.27 mM, are in good agreement with values observed for phosphoketolase from other organisms.The level of phosphoketolase in lithotrophically grown T. novellus was observed to be much lower, 0.002 mol triose formed min^-1 (mg protein)^-1 than the level in heterotrophically grown cells. T. thioparus, a lithotroph, and T. intermedius, a mixotroph, were examined and found not to contain phosphoketolase. T. A2, a mixotroph reported to be very similar to T. novellus, was examined and found to have about 20% of the level of phosphoketolase as that seen in heterotrophically grown T. novellus.Fructose-6-phosphate was examined as a possible alternate substrate but was found not to be enzymatically cleaved in our system.It therefore appears that T. novellus utilizes a previously unknown combination of a partially complete hexose monophosphate pathway, the phosphoketolase reaction, and a partially complete Embden-Meyerhof-Parnas pathway, in conjunction with the Krebs Cycle, for glucose catabolism.     

Glucose metabolism by brown trout peripheral blood lymphocytes

Glucose metabolism in peripheral blood lymphocytes from the brown trout Salmo trutta has been studied. Glucose is taken up by means of a sodium-independent saturable process (K _m=10.8 mmol·l^-1), as well as by simple diffusion. Once within the cell, most of glucose is directed to lactate production through either the Embden-Meyerhof pathway or the hexose-monophosphate shunt. Rates of lactate formation are higher than rates of CO₂ formation. Glutamine does not exert an effect on either glucose uptake or glucose metabolism. The present study provides information regarding the nature of energy sources for different cell types in salmonids.Abbreviations 3-OMG 3-O-methyl glucose - EM Embden-Meyerhoff pathway - G6D glucose-6-phosphate dehydrogenase - HK hexokinase - HMS hexose monophosphate shunt - ICDH isocitrate dehydrogenase - K _m apparent Michaelis constant - LDH lactate dehydrogenase - MCB modified Cortland buffer - PBL peripheral blood lymphocytes - PFK fructose-6-phosphate kinase - PK pyruvate kinase - RBC red blood cells - V _max maximal rate of uptake     

Catabolism of carbohydrates and organic acids and expression of nitrogenase by azospirilla

Fructose, galactose, L-arabinose, gluconate, and several organic acids support rapid growth and N2 fixation of Azospirillum brasiliense ATCC 29145 (strain Sp7) as a sole source of carbon and energy. Growth of Azospirillum lipoferum ATCC 29707 (strain Sp59b) is also supported by glucose, mannose, mannitol, and alpha-ketoglutarate. Oxidation of fructose and gluconate by A. brasiliense Sp7 and of glucose, gluconate, and fructose by A. lipoferum Sp59b was achieved through inducible enzymatic mechanisms. Both strains exhibited all of the enzymes of the Embden-Meyerhof-Parnas pathway, and strain Sp59b also possesses all the enzymes of the Entner-Doudoroff pathway. Fluoride inhibited growth on fructose (strains Sp7 and Sp59b) or on glucose (strain Sp59b) but not on malate. There was no activity via the oxidative hexose monophosphate pathway in either strain. There was greater activity with 1-phosphofructokinase than with 6-phosphofructokinase in both strains. Strain Sp59b formed fructose-6-phosphate via hexokinase, an enzyme that is lacking in strain Sp7. A. brasiliense and A. lipoferum exhibited the enzymes both of the tricarboxylic acid cycle and of the glyoxylate shunt; iodoacetate, fluoropyruvate, and malonate were inhibitory. A. brasiliense Sp7 could not transport [14C]glucose and alpha-[14C]ketoglutarate into its cells.