Catabolism of aspartate and asparagine byBacteroides intermedius andBacteroides gingivalis

Aspartate as asparagine catabolism was studied in representative strains ofBacteroides intermedius strain T588 andB. gingivalis strain W83. Cell suspensions of both species deamidated asparagine. The enzyme asparaginase was constitutive and was unaffected by the addition of ammonium ions to the culture medium. The enzyme aspartase was not detected, but since malate dehydrogenase was known to occur and succinate was present as a major end product of metabolism, aspartate catabolism was postulated to occur via oxaloacetate, malate, and fumarate to succinate. All enzymes of this pathway were present in cell-free extracts, and some of the major properties of these enzymes were examined. The electron carriers cytochrome b and menaquinone-9 were present inB. gingivalis, whereasB. intermedius possessed cytochrome c and menaquinone-11. The membrane-bound enzyme fumarate reductase utilized NADH as an electron donor, but the reaction was inhibited by short wave ultraviolet radiation and 2-n-heptyl-4-hydroxyquinoline-N-oxide.     

Utilization in vivo of glucose and volatile fatty acids by sheep brain for the synthesis of acidic amino acids

1. Free glutamic acid, aspartic acid, glutamic acid from glutamine and, in some instances, the glutamic acid from glutathione and the aspartic acid from N-acetyl-aspartic acid were isolated from the brains of sheep and assayed for radioactivity after intravenous injection of [2-¹⁴C]glucose, [1-¹⁴C]acetate, [1-¹⁴C]butyrate or [2-¹⁴C]propionate. These brain components were also isolated and analysed from rats that had been given [2-¹⁴C]propionate. The results indicate that, as in rat brain, glucose is by far the best precursor of the free amino acids of sheep brain. 2. Degradation of the glutamate of brain yielded labelling patterns consistent with the proposal that the major route of pyruvate metabolism in brain is via acetyl-CoA, and that the short-chain fatty acids enter the brain without prior metabolism by other tissue and are metabolized in brain via the tricarboxylic acid cycle. 3. When labelled glucose was used as a precursor, glutamate always had a higher specific activity than glutamine; when labelled fatty acids were used, the reverse was true. These findings add support and complexity to the concept of the metabolic `compartmentation' of the free amino acids of brain. 4. The results from experiments with labelled propionate strongly suggest that brain metabolizes propionate via succinate and that this metabolic route may be a limited but important source of dicarboxylic acids in the brain.     

Schistosoma mansoni and Schistosoma japonicum: Utilization of amino acids

, , and 1972. Schistosoma mansoni and Schistosoma japonicum: utilization of amino acids. International Journal for Parasitology 2: 425–430. The production of ¹⁴CO₂ from 12 labeled amino acids by S. mansoni and S. japonicum was studied. No ¹⁴CO₂ was detected from incubations with glycine, isoleucine, leucine, lysine or phenylalanine. Differences were found between sexes and/or species for the other amino acids studied. Species related differences included a greater rate of metabolism of glutamic and aspartic acid by S. mansoni than by S. japonicum. Proline and histidine were utilized by S. mansoni males and females, respectively. S. japonicum male worms did not utilize proline, while histidine was not utilized by the female of this species. Major sex related differences included greater ¹⁴CO₂ production from glutamic acid, aspartic acid and arginine by S. mansoni males than by females, and the utilization of histidine by male S. japonicum but not by females. Incubation in tyrosine resulted in the release of only small amounts of ¹⁴CO₂ by female worms of both species but no ¹⁴CO₂ production by male worms.     

浅析单体氨基酸、核苷酸和葡萄糖

分类比较了单体氨基酸核苷酸和葡萄糖,对学生全面理解这3种物质有帮助。     

Utilization of amino acids by Chromatium sp. strain D

Summary The duration of various morphologically distinct phases in the division cycle of the marine heterotroph Cryptothecodinium cohnii was measured in cultures initiated with synchronously excysted swarmer cells. Parent cysts were selectively isolated on plastic surfaces and progeny of a narrow age distribution harvested in a specifically conditioned medium. The swarmer phase, an interval of predivisional encystment, daughter cell formation and excystment were 5.0, 3.0 and 2.0 h respectively. Two major kinds of cytokinesis (production of 2 and 4 daughter cells) were observed resulting in a mean daughter cell number of 2.7 under these conditions. Other growth parameters for this dinoflagellate are described.     

Food intake of suckling rats after administration of glucose and amino acids

The changes of food intake after administration of glucose or a mixture of amino acids were determined in rat pups from the 5th to the 23rd day of life. The milk intake was significantly reduced 90 min after glucose treatment in 17 day-old pups, while decreased food intake after injection of aminoacids was observed only after the 23rd day of life. It is being concluded that the regulation of food intake in correlation to the blood concentrations of various key metabolic factors develops gradually during the suckling period, depending on the development of the CNS and on changes in diet composition.     

Bacteroides gingivalis and Bacteroides intermedius recognize different sites on human fibrinogen.

Bacteroides (Porphyromonas) gingivalis and Bacteroides (Porphyromonas) intermedius have been implicated in the etiology of human periodontal diseases. These organisms are able to bind and degrade human fibrinogen, and these interactions may play a role in the pathogenesis of periodontal disease. In attempts to map the bacterial binding sites along the fibrinogen molecule, we have found that strains of B. gingivalis and B. intermedius, respectively, recognize spatially distant and distinct sites on the fibrinogen molecule. Isolated reduced and alkylated alpha-, beta-, and gamma-fibrinogen chains inhibited binding of 125I-fibrinogen to both Bacteroides species in a concentration-dependent manner. Plasmin fragments D and to some extent fragment E, however, produced a concentration-dependent inhibition of 125I-fibrinogen binding to B. intermedius strains but did not affect binding of 125I-fibrinogen to B. gingivalis strains. Radiolabeled fibrinogen chains and fragments were compared with 125I-fibrinogen with respect to specificity and reversibility of binding to bacteria. According to these criteria, gamma chain most closely resembled the native fibrinogen molecule in behavior toward B. gingivalis strains and fragments D most closely resembled fibrinogen in behavior toward B. intermedius strains. The ability of anti-human fibrinogen immunoglobulin G (IgG) to inhibit binding of 125I-fibrinogen to B. intermedius strains was greatly reduced by absorbing the IgG with fragments D. Absorbing the IgG with fragments D had no effect on the ability of the antibody to inhibit binding of 125I-fibrinogen to B. gingivalis strains. A purified staphylococcal fibrinogen-binding protein blocked binding of 125I-fibrinogen to B. intermedius strains but not to B. gingivalis strains.     

Utilization of glucose and amino acids in insect cell cultures: Quantifying the metabolic flows within the primary pathways and medium development

The current understanding of insect cell metabolism is very limited. In order to gain some insight into the growth and metabolism of insect cells Spodoptera frugiperda (Sf9), a comprehensive characterization of culture conditions for cells grown in the IPL-41 medium was made by measuring the amino acid composition of the growth medium and the cell extract, the macromolecular composition of the cells (DNA, RNA, and protein), medium concentrations of various metabolites and sugars, and the evolved CO(2). Since in the IPL-41-based serum-free medium all of the amino acids except cysteine are in great excess of what is needed by the cells for energy and protein production, a medium formulation with an osmolarity similar to the IPL-41 but with a lower amino acid content than IPL-41 was also developed. The new medium also lacks maltose and sucrose (contains only glucose), supported cell growth to a high cell density of 8 x 10(6) cells/mL. The cellular and energetic yields indicated that a tight coupling between the biosynthetic and energetic reactions was attained for cells grown in the new medium. Moreover, it was found that the intermittent feeding of glucose may not be required as the cell yield and growth rate were comparable whether the same total amount of glucose was provided intermittently or was included initially in the medium. The eventual cessation of growth in the new medium is believed to be due to the amino acid limitation because concentrations of both glutamine and glutamate were very low at the end of the growth phase. Thus, further optimization, which may include higher initial glutamine in the medium or its intermittent feeding, could lead to a further increase in the cell density. Finally, a stoichiometrically based analysis of metabolic reactions confirmed the operation of the key pathways and was used to quantify the distribution of metabolites among primary metabolic reactions. The quantitative flow values were used to highlight some key aspects of insect cell metabolism. (c) 1993 John Wiley & Sons, Inc.     

The effect of 2-oxoglutarate and biotin in the release of amino acids by Citrobacter intermedius C3

Excretion of amino acids by Citrobacter intermedius C3 was assayed in a mineral medium with glucose as carbon source. Glutamic acid is the main amino acid excreted in liquid medium and it is also detected at the colonial level in solid medium. Mutants with different behaviour with respect to the excretion of amino acids are studied. The presence of 2-oxoglutarate in the medium induced excretion in all strains. On the other hand when biotin was added to the culture media amino acid excretion was partially reduced.