Glyceric Acids
Gluconobacter
Dihydroxyacetone
Comfrey
Ultrasensitive glycogen synthesis in Cyanobacteria. (1/191)
Cyanobacter ADPglucose pyrophosphorylase exhibits a ultrasensitive response in activity towards its allosteric effector 3-phosphoglycerate, elicited by orthophosphate and polyethyleneglycol-induced molecular crowding. The ultrasensitive response was observed either when the enzyme operates in the zero or first order region for its physiological substrates. The ultrasensitivity exhibited maximal amplification factors of 15-19-fold with respect to 1% of the maximal system velocity. Only a 2.4-3.8-fold increase in 3PGA concentration was necessary to augment the flux from 10% to 90% through AGPase as compared with 200-fold required for the control. The results are discussed in terms of finely tuned regulatory mechanisms of polysaccharide synthesis in oxygenic photosynthetic organisms. (+info)A phosphoglycerate to inorganic phosphate ratio is the major factor in controlling starch levels in chloroplasts via ADP-glucose pyrophosphorylase regulation. (2/191)
Purified barley leaf ADP-glucose pyrophosphorylase, a key enzyme of the starch synthesis in the chloroplast stroma, was analysed with respect to its possible regulation by factors defining the metabolic/effector status of the chloroplast during light and dark conditions. The enzyme required 3-phosphoglyceric acid for the maximal activity and was inhibited by inorganic phosphate. The optimal pH for the enzyme was at circa 7.0, regardless of the presence or absence of 3-phosphoglyceric acid, whereas the maximal activation by 3-phosphoglyceric acid was observed at pH 8.5 and higher. Changes in the concentration of Mg2+ and dithiothreitol had little or no effect on the enzymatic activity of AGPase. It has been directly demonstrated for the first time that a 3-phosphoglyceric acid/inorganic phosphate ratio, a crucial regulatory parameter, could be directly related to a defined activation state of the enzyme, allowing the prediction of a relative AGPase activity under given conditions. The predicted changes in the enzyme activity were directly correlated with earlier reported responses of starch levels to the 3-phosphoglyceric acid/inorganic phosphate ratio in chloroplasts. Consequences of this for the starch biosynthesis are discussed. (+info)A rectifying ATP-regulated solute channel in the chloroplastic outer envelope from pea. (3/191)
Phosphorylated carbohydrates are the main photoassimilated export products from chloroplasts that support the energy household and metabolism of the plant cell. Channels formed by the chloroplastic outer envelope protein OEP21 selectively facilitate the translocation of triosephosphate, 3-phosphoglycerate and phosphate, central intermediates in the source-sink relationship between the chloroplast and the cytosol. The anion selectivity and asymmetric transport properties of OEP21 are modulated by the ratio between ATP and triosephosphates, 3-phosphoglycerate and phosphate in the intermembrane space. Conditions that lead to export of triosephosphate from chloroplasts, i.e. photosynthesis, result in outward-rectifying OEP21 channels, while a high ATP to triosephosphate ratio, e.g. dark metabolism, leads to inward-rectifying OEP21 channels with a less pronounced anion selectivity. We conclude that solute exchange between plastids and cytosol can already be regulated at the level of the organellar outer membrane. (+info)Biosynthesis of mannosylglycerate in the thermophilic bacterium Rhodothermus marinus. Biochemical and genetic characterization of a mannosylglycerate synthase. (4/191)
The biosynthetic reaction scheme for the compatible solute mannosylglycerate in Rhodothermus marinus is proposed based on measurements of the relevant enzymatic activities in cell-free extracts and in vivo (13)C labeling experiments. The synthesis of mannosylglycerate proceeded via two alternative pathways; in one of them, GDP mannose was condensed with D-glycerate to produce mannosylglycerate in a single reaction catalyzed by mannosylglycerate synthase, in the other pathway, a mannosyl-3-phosphoglycerate synthase catalyzed the conversion of GDP mannose and D-3-phosphoglycerate into a phosphorylated intermediate, which was subsequently converted to mannosylglycerate by the action of a phosphatase. The enzyme activities committed to the synthesis of mannosylglycerate were not influenced by the NaCl concentration in the growth medium. However, the combined mannosyl-3-phosphoglycerate synthase/phosphatase system required the addition of NaCl or KCl to the assay mixture for optimal activity. The mannosylglycerate synthase enzyme was purified and characterized. Based on partial sequence information, the corresponding mgs gene was identified from a genomic library of R. marinus. In addition, the mgs gene was overexpressed in Escherichia coli with a high yield. The enzyme had a molecular mass of 46,125 Da, and was specific for GDP mannose and D-glycerate. This is the first report of the characterization of a mannosylglycerate synthase. (+info)Is leaf ADP-glucose pyrophosphorylase an allosteric enzyme? (5/191)
Barley leaf ADP-glucose pyrophosphorylase (AGPase), a key enzyme of starch synthesis in the chloroplast stroma, was analysed, in both directions of the reaction, with respect to details of its regulation by 3-phosphoglycerate (PGA) and inorganic phosphate (Pi) which serve as activator and inhibitor, respectively. AGPase was found to catalyse a close-to-equilibrium reaction, with the K(eq) value of approximately 0.5, i.e. slightly favouring the pyrophosphorolytic direction. When the enzyme was analysed by substrate kinetics, PGA acted either as a linear (hyperbolic response) 'non-competitive' activator (forward reaction) or a linear near-'competitive' activator (reverse reaction). When the activation and inhibition patterns with PGA and Pi, respectively, were studied in detail by Dixon plots, the response curves to effectors also followed hyperbolic kinetics, with the experimentally determined K(a) and K(i) values on the order of micromolar. The results suggest that the regulation of AGPase proceeds via a non-cooperative mechanism, where neither of the effectors, when considered separately, induces any allosteric response. The evidence, discussed in terms of an overall kinetic mechanism/regulation of leaf AGPase, prompts caution in classifying the protein as an 'allosteric enzyme'. (+info)Locations of the regulatory sites for isocitrate dehydrogenase kinase/phosphatase. (6/191)
Isocitrate dehydrogenase (IDH)(1) of Escherichia coli is regulated by a bifunctional protein, IDH kinase/phosphatase. In this paper, we demonstrate that the effectors controlling these activities belong to two distinct classes that differ in mechanism and in the locations of their binding sites. NADPH and isocitrate are representative members of one of these effector classes. NADPH inhibits both IDH kinase and IDH phosphatase, whereas isocitrate inhibits only IDH kinase. Isocitrate can "activate" IDH phosphatase by reversing product inhibition by dephospho-IDH. Mutations in icd, which encodes IDH, had parallel effects on the binding of these ligands to the IDH active site and on their effects on IDH kinase and phosphatase, indicating that these ligands regulate IDH kinase/phosphatase through the IDH active site. Kinetic analyses suggested that isocitrate and NADPH prevent formation of the complex between IDH kinase/phosphatase and its protein substrate. AMP, 3-phosphoglycerate, and pyruvate represent a class of regulatory ligands that is distinct from that which includes isocitrate and NADPH. These ligands bind directly to IDH kinase/phosphatase, a conclusion which is supported by the observation that they inhibit the IDH-independent ATPase activity of this enzyme. These effector classes can also be distinguished by the observation that mutant derivatives of IDH kinase/phosphatase expressed from aceK3 and aceK4 exhibited dramatic changes in their responses to AMP, 3-phosphoglycerate, and pyruvate but not to NADPH and isocitrate. (+info)Activation of the potato tuber ADP-glucose pyrophosphorylase by thioredoxin. (7/191)
The potato tuber (Solanum tuberosum L.) ADP-glucose pyrophosphorylase (ADP-GlcPPase) catalyzes the first committed step in starch biosynthesis. The main type of regulation of this enzyme is allosteric, and its activity is controlled by the ratio of activator, 3-phosphoglycerate to inhibitor, P(i). It was reported (Fu, Y., Ballicora, M. A., Leykam, J. F., and Preiss, J. (1998) J. Biol. Chem. 273, 25045-25052) that the enzyme was activated by reduction of the Cys(12) disulfide linkage present in the catalytic subunits. In this study, both reduced thioredoxin f and m from spinach (Spinacia oleracea) leaves reduced and activated the enzyme at low concentrations (10 microM) of activator (3-phosphoglycerate). Fifty percent activation was at 4.5 and 8.7 microM for reduced thioredoxin f and m, respectively, and 2 orders of magnitude lower than for dithiothreitol. The activation was reversed by oxidized thioredoxin. Cys(12) is conserved in the ADP-GlcPPases from plant leaves and other tissues except for the monocot endosperm enzymes. We postulate that in photosynthetic tissues, reduction could play a role in the fine regulation of the ADP-GlcPPase mediated by the ferredoxin-thioredoxin system. This is the first time that a covalent mechanism of regulation is postulated in the synthesis of starch. (+info)A common regulator for the operons encoding the enzymes involved in D-galactarate, D-glucarate, and D-glycerate utilization in Escherichia coli. (8/191)
Genes for D-galactarate (gar) and D-glucarate (gud) metabolism in Escherichia coli are organized in three transcriptional units: garD, garPLRK, and gudPD. Two observations suggested a common regulator for the three operons. (i) Their expression was triggered by D-galactarate, D-glucarate, and D-glycerate. (ii) Metabolism of the three compounds was impaired by a single Tn5 insertion mapped in the yaeG gene (proposed name, sdaR), outside the D-galactarate and D-glucarate systems. Expression of the sdaR gene is autogenously regulated. (+info)I believe there might be a slight misunderstanding in your question. "Glyceric acid" is not a widely recognized or established term in medicine or biochemistry. However, glyceric acid can refer to a specific compound with the chemical formula C3H8O4, also known as 2,3-dihydroxypropanoid acid or glycerol-3-phosphate when phosphorylated.
Glyceric acid is an organic compound that plays a crucial role in cellular metabolism, particularly in energy production pathways such as glycolysis and gluconeogenesis. It can be formed from the reduction of dihydroxyacetone phosphate (a glycolytic intermediate) or through the oxidation of glycerol.
If you were referring to a different term or concept, please provide more context so I can give a more accurate answer.
"Gluconobacter" is a genus of gram-negative, aerobic bacteria that are capable of oxidizing various alcohols and sugars into their corresponding acids. These bacteria are often found in fruit, flowers, and sap, as well as in fermented foods and beverages. They are known for their ability to rapidly and efficiently oxidize glucose into gluconic acid, which gives them their name. Some species of Gluconobacter can also cause disease in humans, particularly in individuals with weakened immune systems. In medical contexts, Gluconobacter species may be associated with infections such as bacteremia, endocarditis, and peritonitis.
Dihydroxyacetone (DHA) is a simple sugar that is used as an ingredient in many self-tanning products. When applied to the skin, DHA reacts with amino acids in the dead layer of the skin to temporarily darken the skin color. This process is known as the Maillard reaction, which is a chemical reaction between an amino acid and a sugar. The effect of DHA is limited to the uppermost layer of the skin and it does not provide any protection against sunburn or UV radiation. The tanning effect produced by DHA usually lasts for about 5-7 days.
It's important to note that while DHA is considered safe for external use, it should not be inhaled or ingested, as it can cause irritation and other adverse effects. Additionally, some people may experience skin irritation or allergic reactions to products containing DHA, so it's always a good idea to do a patch test before using a new self-tanning product.
Comfrey is a plant species (Symphytum spp.) that has been used in traditional medicine for its alleged healing properties, particularly for treating inflammation and promoting wound healing. However, it's important to note that the use of comfrey has been associated with serious health risks, including liver damage and cancer.
The active constituents of comfrey include allantoin, rosmarinic acid, and tannins, among others. Allantoin is believed to have anti-inflammatory and wound-healing effects, while rosmarinic acid has antioxidant properties. However, comfrey also contains pyrrolizidine alkaloids (PAs), which can be toxic to the liver and other organs.
Due to these risks, the use of comfrey for medicinal purposes is not recommended by many health organizations, including the US Food and Drug Administration (FDA) and the National Center for Complementary and Integrative Health (NCCIH). Topical creams and ointments containing comfrey may be available over-the-counter in some countries, but they should be used with caution and only under the guidance of a healthcare professional.
In summary, while comfrey has been used historically for its medicinal properties, its use is not recommended due to the potential health risks associated with its toxic compounds.
Glycerol, also known as glycerine or glycerin, is a simple polyol (a sugar alcohol) with a sweet taste and a thick, syrupy consistency. It is a colorless, odorless, viscous liquid that is slightly soluble in water and freely miscible with ethanol and ether.
In the medical field, glycerol is often used as a medication or supplement. It can be used as a laxative to treat constipation, as a source of calories and energy for people who cannot eat by mouth, and as a way to prevent dehydration in people with certain medical conditions.
Glycerol is also used in the production of various medical products, such as medications, skin care products, and vaccines. It acts as a humectant, which means it helps to keep things moist, and it can also be used as a solvent or preservative.
In addition to its medical uses, glycerol is also widely used in the food industry as a sweetener, thickening agent, and moisture-retaining agent. It is generally recognized as safe (GRAS) by the U.S. Food and Drug Administration (FDA).