Fructose-Bisphosphatase
Chloroplasts
Fructose
Phosphofructokinase-2
Fructosediphosphates
Hexosediphosphates
Fructosephosphates
Phosphoric Monoester Hydrolases
Phosphofructokinase-1
Phosphotransferases
Inhibitory sites in enzymes: zinc removal and reactivation by thionein. (1/523)
Thionein (T) has not been isolated previously from biological material. However, it is generated transiently in situ by removal of zinc from metallothionein under oxidoreductive conditions, particularly in the presence of selenium compounds. T very rapidly activates a group of enzymes in which zinc is bound at an inhibitory site. The reaction is selective, as is apparent from the fact that T does not remove zinc from the catalytic sites of zinc metalloenzymes. T instantaneously reverses the zinc inhibition with a stoichiometry commensurate with its known capacity to bind seven zinc atoms in the form of clusters in metallothionein. The zinc inhibition is much more pronounced than was previously reported, with dissociation constants in the low nanomolar range. Thus, T is an effective, endogenous chelating agent, suggesting the existence of a hitherto unknown and unrecognized biological regulatory system. T removes the metal from an inhibitory zinc-specific enzymatic site with a resultant marked increase of activity. The potential significance of this system is supported by the demonstration of its operations in enzymes involved in glycolysis and signal transduction. (+info)Expression and regulation of 6-phosphofructo-2-kinase/fructose- 2,6-bisphosphatase isozymes in white adipose tissue. (2/523)
The aim of this work was to identify the 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2) isozyme(s) present in white adipose tissue. Ion-exchange chromatography of PFK-2 from rat epididymal fat pads yielded an elution pattern compatible with the presence of both the L (liver) and M (muscle) isozymes. This was consistent with a study of the phosphorylation of the purified adipose tissue enzyme by cAMP-dependent protein kinase, by specific labelling of the preparation with [2-32P]fructose 2,6-bisphosphate and by reaction with antibodies. Characterization of the PFK-2/FBPase-2 mRNAs showed that mature adipocytes express the mRNA that codes for the L isozyme and the two mRNAs that code for the M isozyme. Preadipocytes expressed mRNA that codes for the M isozyme. Incubation of rat epididymal fat pads with adrenaline stimulated glycolysis but decreased fructose 2,6-bisphosphate concentrations without significant inactivation of PFK-2. These results support previous findings showing that fructose 2,6-bisphosphate is not involved in the adrenaline-induced stimulation of glycolysis in white adipose tissue. (+info)Cyclic AMP can decrease expression of genes subject to catabolite repression in Saccharomyces cerevisiae. (3/523)
External cyclic AMP (cAMP) hindered the derepression of gluconeogenic enzymes in a pde2 mutant of Saccharomyces cerevisiae, but it did not prevent invertase derepression. cAMP reduced nearly 20-fold the transcription driven by upstream activation sequence (UAS1FBP1) from FBP1, encoding fructose-1,6-bisphosphatase; it decreased 2-fold the activation of transcription by UAS2FBP1. Nuclear extracts from cells derepressed in the presence of cAMP were impaired in the formation of specific UASFBP1-protein complexes in band shift experiments. cAMP does not appear to act through the repressing protein Mig1. Control of FBP1 transcription through cAMP is redundant with other regulatory mechanisms. (+info)Dehydroepiandrosterone suppresses the elevated hepatic glucose-6-phosphatase and fructose-1,6-bisphosphatase activities in C57BL/Ksj-db/db mice: comparison with troglitazone. (4/523)
The effect of dehydroepiandrosterone (DHEA) on the hepatic and muscle glucose metabolizing enzymes and on blood glucose were investigated in insulin-resistant diabetic C57BL/KsJ-db/db mice and their heterozygote littermates (db/+m). The results were compared with those after troglitazone administration under the same conditions. Despite hyperinsulinemia, hepatic glucose-6-phosphatase (G6Pase) and fructose-1,6-bisphosphatase (FBPase) activities are higher in db/db than in db/+m mice. Dietary administration of DHEA and that of troglitazone for 15 days to respective groups of five mice each significantly decreased blood glucose in db/db mice and hepatic G6Pase and FBPase activities in both db/db and db/+m mice. Hepatic G6Pase and FBPase activities showed a linear relationship with blood glucose in all groups of mice, suggesting that the activities of G6Pase and FBPase are closely related to blood glucose levels. Because androstenedione, a DHEA metabolite, barely affected either of these enzyme activities or blood glucose in db/db mice, the actions of DHEA, which are similar to those of troglitazone, are presumed to be caused by DHEA itself. DHEA is considered to be a modulating agent for the activities of hepatic gluconeogenic enzymes in db/db mice. (+info)Regulation of exopolysaccharide production by Lactococcus lactis subsp. cremoris By the sugar source. (5/523)
Lactococcus lactis produced more exopolysaccharide (EPS) on glucose than on fructose as the sugar substrate, although the transcription level of the eps gene cluster was independent of the sugar source. A major difference between cells grown on the two substrates was the capacity to produce sugar nucleotides, the EPS precursors. However, the activities of the enzymes required for the synthesis of nucleotide sugars were not changed upon growth on different sugars. The activity of fructosebisphosphatase (FBPase) was by far the lowest of the enzymes involved in precursor formation under all conditions. FBPase catalyzes the conversion of fructose-1, 6-diphosphate into fructose-6-phosphate, which is an essential step in the biosynthesis of sugar nucleotides from fructose but not from glucose. By overexpression of the fbp gene, which resulted in increased EPS synthesis on fructose, it was proven that the low activity of FBPase is indeed limiting not only for EPS production but also for growth on fructose as a sugar source. (+info)Tissue-specific alternative splicing of rat brain fructose 6-phosphate 2-kinase/fructose 2,6-bisphosphatase. (6/523)
We have reported the occurrence of eight splice variants of rat brain fructose 6-phosphate 2-kinase/fructose 2,6-bisphosphatase (RB2K). In the present study, we quantified these splice variants in various tissues using a RNAse protection assay and found a tissue-specific pattern of alternative splicing of the RB2K gene. Splice variants containing exon F were specifically expressed in brain. Moreover, exons D and E were spliced in brain, skeletal muscle and heart. Consequently, eight, six, four and two splice variants were expressed in brain, skeletal muscle, heart and liver plus testis, respectively. These results suggest that distinct RB2K isoforms could be involved in regulation of glycolysis in a tissue-specific manner. (+info)Redox signalling in the chloroplast: structure of oxidized pea fructose-1,6-bisphosphate phosphatase. (7/523)
Sunlight provides the energy source for the assimilation of carbon dioxide by photosynthesis, but it also provides regulatory signals that switch on specific sets of enzymes involved in the alternation of light and dark metabolisms in chloroplasts. Capture of photons by chlorophyll pigments triggers redox cascades that ultimately activate target enzymes via the reduction of regulatory disulfide bridges by thioredoxins. Here we report the structure of the oxidized, low-activity form of chloroplastic fructose-1, 6-bisphosphate phosphatase (FBPase), one of the four enzymes of the Calvin cycle whose activity is redox-regulated by light. The regulation is of allosteric nature, with a disulfide bridge promoting the disruption of the catalytic site across a distance of 20 A. Unexpectedly, regulation of plant FBPases by thiol-disulfide interchange differs in every respect from the regulation of mammalian gluconeogenic FBPases by AMP. We also report a second crystal form of oxidized FBPase whose tetrameric structure departs markedly from D(2) symmetry, a rare event in oligomeric structures, and the structure of a constitutively active mutant that is unable to form the regulatory disulfide bridge. Altogether, these structures provide a structural basis for redox regulation in the chloroplast. (+info)Induction of a futile Embden-Meyerhof-Parnas pathway in Deinococcus radiodurans by Mn: possible role of the pentose phosphate pathway in cell survival. (8/523)
Statistical models were used to predict the effects of tryptone, glucose, yeast extract (TGY) and Mn on biomass formation of the highly radioresistant bacterium Deinococcus radiodurans. Results suggested that glucose had marginal effect on biomass buildup, but Mn was a significant factor for biomass formation. Mn also facilitated glucose interactions with other nutrient components. These predictions were verified by in vivo and in vitro experiments. TGY-grown cells metabolized glucose solely by the pentose phosphate pathway (PPP). Although only a fraction of glucose from the medium was transported into the cells, glucose was incorporated into the DNA efficiently after cells were exposed to UV light. The presence of glucose also enhanced the radioresistance of the culture. Mn could induce an Embden-Meyerhof-Parnas (EMP) pathway in D. radiodurans. The EMP pathway and the PPP of the Mn-treated cells oxidized glucose simultaneously at a 6:1 ratio. Although glucose was hydrolyzed rapidly by the Mn-treated cells, most glucose was released as CO(2). Mn-treated cultures retained less glucose per cell than cells grown without Mn, and still less glucose was incorporated into the DNA after cells were exposed to UV light. Mn-treated cells were also more sensitive to UV light. Results suggested that metabolites of glucose generated from the PPP enhanced the survival of D. radiodurans. Induction of the EMP pathway by Mn may deplete metabolites for DNA repair and may induce oxidative stress for the cell, leading to reduction of radioresistance. (+info)Fructose-bisphosphatase (FBPase) is an enzyme that plays a crucial role in the regulation of gluconeogenesis, which is the process of generating new glucose molecules from non-carbohydrate sources in the body. Specifically, FBPase is involved in the fourth step of gluconeogenesis, where it catalyzes the conversion of fructose-1,6-bisphosphate to fructose-6-phosphate.
Fructose-1,6-bisphosphate is a key intermediate in both glycolysis and gluconeogenesis, and its conversion to fructose-6-phosphate represents an important regulatory point in these pathways. FBPase is inhibited by high levels of energy charge (i.e., when the cell has plenty of ATP and low levels of ADP), as well as by certain metabolites such as citrate, which signals that there is abundant energy available from other sources.
There are two main isoforms of FBPase in humans: a cytoplasmic form found primarily in the liver and kidney, and a mitochondrial form found in various tissues including muscle and brain. Mutations in the gene that encodes the cytoplasmic form of FBPase can lead to a rare inherited metabolic disorder known as fructose-1,6-bisphosphatase deficiency, which is characterized by impaired gluconeogenesis and hypoglycemia.
Chloroplasts are specialized organelles found in the cells of green plants, algae, and some protists. They are responsible for carrying out photosynthesis, which is the process by which these organisms convert light energy from the sun into chemical energy in the form of organic compounds, such as glucose.
Chloroplasts contain the pigment chlorophyll, which absorbs light energy from the sun. They also contain a system of membranes and enzymes that convert carbon dioxide and water into glucose and oxygen through a series of chemical reactions known as the Calvin cycle. This process not only provides energy for the organism but also releases oxygen as a byproduct, which is essential for the survival of most life forms on Earth.
Chloroplasts are believed to have originated from ancient cyanobacteria that were engulfed by early eukaryotic cells and eventually became integrated into their host's cellular machinery through a process called endosymbiosis. Over time, chloroplasts evolved to become an essential component of plant and algal cells, contributing to their ability to carry out photosynthesis and thrive in a wide range of environments.
Fructose is a simple monosaccharide, also known as "fruit sugar." It is a naturally occurring carbohydrate that is found in fruits, vegetables, and honey. Fructose has the chemical formula C6H12O6 and is a hexose, or six-carbon sugar.
Fructose is absorbed directly into the bloodstream during digestion and is metabolized primarily in the liver. It is sweeter than other sugars such as glucose and sucrose (table sugar), which makes it a popular sweetener in many processed foods and beverages. However, consuming large amounts of fructose can have negative health effects, including increasing the risk of obesity, diabetes, and heart disease.
Phosphofructokinase-2 (PFK-2) is an enzyme that plays a crucial role in regulating the rate of glycolysis, which is the metabolic pathway responsible for the conversion of glucose into energy. PFK-2 catalyzes the phosphorylation of fructose-6-phosphate to form fructose-1,6-bisphosphate and subsequently fructose-2,6-bisphosphate (F-2,6-BP). F-2,6-BP is a potent allosteric activator of another enzyme called phosphofructokinase-1 (PFK-1), which is the rate-limiting enzyme in glycolysis.
PFK-2 exists as a complex with another enzyme, fructose-2,6-bisphosphatase (FBPase-2), and together they form a bifunctional enzyme called PFK-2/FBPase-2. This enzyme can reversibly convert F-6-P to F-2,6-BP and vice versa depending on the cellular energy status. When cells have high energy levels, FBPase-2 is activated, which leads to a decrease in F-2,6-BP levels and an inhibition of glycolysis. Conversely, when cells require more energy, PFK-2 is activated, leading to an increase in F-2,6-BP levels and an activation of glycolysis.
Regulation of PFK-2 activity occurs through various mechanisms, including allosteric regulation by metabolites such as AMP, citrate, and phosphate, as well as covalent modification by protein kinases and phosphatases. Dysregulation of PFK-2 has been implicated in several diseases, including diabetes, cancer, and neurological disorders.
I'm sorry for any confusion, but "Fructosediphosphates" is not a recognized term in medicine or biochemistry. It's possible there may be a spelling mistake or misunderstanding in the term you're looking for.
If you meant "Fructose 1,6-bisphosphate," that is a key intermediate in carbohydrate metabolism. It's formed from fructose 6-phosphate in the process of glucose breakdown (glycolysis) and is then used in the generation of energy through the citric acid cycle.
If these terms are not what you were looking for, could you please provide more context or check the spelling? I'm here to help!
Hexose diphosphates refer to a class of organic compounds that consist of a hexose sugar molecule (a monosaccharide containing six carbon atoms) linked to two phosphate groups. The most common examples of hexose diphosphates are glucose 1,6-bisphosphate and fructose 1,6-bisphosphate, which play important roles in cellular metabolism.
Glucose 1,6-bisphosphate is involved in the regulation of glycolysis, a process by which glucose is broken down to produce energy in the form of ATP. It acts as an allosteric regulator of several enzymes involved in this pathway and helps to maintain the balance between different metabolic processes.
Fructose 1,6-bisphosphate, on the other hand, is a key intermediate in gluconeogenesis, a process by which cells synthesize glucose from non-carbohydrate precursors. It is also involved in the regulation of glycolysis and helps to control the flow of metabolites through these pathways.
Overall, hexose diphosphates are important regulators of cellular metabolism and play a critical role in maintaining energy homeostasis in living organisms.
Fructose-1,6-bisphosphate (also known as fructose 1,6-diphosphate or Fru-1,6-BP) is the chemical compound that plays a crucial role in cellular respiration and glucose metabolism. It is not accurate to refer to "fructosephosphates" as a medical term, but fructose-1-phosphate and fructose-1,6-bisphosphate are important fructose phosphates with specific functions in the body.
Fructose-1-phosphate is an intermediate metabolite formed during the breakdown of fructose in the liver, while fructose-1,6-bisphosphate is a key regulator of glycolysis, the process by which glucose is broken down to produce energy in the form of ATP. Fructose-1,6-bisphosphate allosterically regulates the enzyme phosphofructokinase, which is the rate-limiting step in glycolysis, and its levels are tightly controlled to maintain proper glucose metabolism. Dysregulation of fructose metabolism has been implicated in various metabolic disorders, including insulin resistance, type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD).
Phosphoric monoester hydrolases are a class of enzymes that catalyze the hydrolysis of phosphoric monoesters into alcohol and phosphate. This class of enzymes includes several specific enzymes, such as phosphatases and nucleotidases, which play important roles in various biological processes, including metabolism, signal transduction, and regulation of cellular processes.
Phosphoric monoester hydrolases are classified under the EC number 3.1.3 by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (IUBMB). The enzymes in this class share a common mechanism of action, which involves the nucleophilic attack on the phosphorus atom of the substrate by a serine or cysteine residue in the active site of the enzyme. This results in the formation of a covalent intermediate, which is then hydrolyzed to release the products.
Phosphoric monoester hydrolases are important therapeutic targets for the development of drugs that can modulate their activity. For example, inhibitors of phosphoric monoester hydrolases have been developed as potential treatments for various diseases, including cancer, neurodegenerative disorders, and infectious diseases.
Phosphofructokinase-1 (PFK-1) is a rate-limiting enzyme in the glycolytic pathway, which is the metabolic pathway that converts glucose into pyruvate, producing ATP and NADH as energy currency for the cell. PFK-1 plays a crucial role in regulating the rate of glycolysis by catalyzing the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate, using ATP as the phosphate donor.
PFK-1 is allosterically regulated by various metabolites, such as AMP, ADP, and ATP, which act as positive or negative effectors of the enzyme's activity. For example, an increase in the intracellular concentration of AMP or ADP can activate PFK-1, promoting glycolysis and energy production, while an increase in ATP levels can inhibit the enzyme's activity, conserving glucose for use under conditions of low energy demand.
Deficiencies in PFK-1 can lead to a rare genetic disorder called Tarui's disease or glycogen storage disease type VII, which is characterized by exercise intolerance, muscle cramps, and myoglobinuria (the presence of myoglobin in the urine due to muscle damage).
Phosphotransferases are a group of enzymes that catalyze the transfer of a phosphate group from a donor molecule to an acceptor molecule. This reaction is essential for various cellular processes, including energy metabolism, signal transduction, and biosynthesis.
The systematic name for this group of enzymes is phosphotransferase, which is derived from the general reaction they catalyze: D-donor + A-acceptor = D-donor minus phosphate + A-phosphate. The donor molecule can be a variety of compounds, such as ATP or a phosphorylated protein, while the acceptor molecule is typically a compound that becomes phosphorylated during the reaction.
Phosphotransferases are classified into several subgroups based on the type of donor and acceptor molecules they act upon. For example, kinases are a subgroup of phosphotransferases that transfer a phosphate group from ATP to a protein or other organic compound. Phosphatases, another subgroup, remove phosphate groups from molecules by transferring them to water.
Overall, phosphotransferases play a critical role in regulating many cellular functions and are important targets for drug development in various diseases, including cancer and neurological disorders.
Chloroplast thioredoxins are small, heat-stable proteins located in the chloroplasts of plant cells. They play a crucial role in regulating various metabolic processes in the chloroplast, particularly those related to photosynthesis. Thioredoxins function as electron carriers and reduce disulfide bonds in target proteins, thereby activating or deactivating their enzymatic activity.
Chloroplast thioredoxins are reduced by ferredoxin-thioredoxin reductase using electrons supplied by photosystem I during light reactions of photosynthesis. This reduction process enables chloroplast thioredoxins to regulate the activity of various enzymes involved in carbon fixation, such as Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase), and other metabolic processes like protein folding and degradation.
There are multiple isoforms of chloroplast thioredoxins (trx), including TrxA, TrxB, TrxC, and TrxD, each with distinct roles in regulating specific target proteins and cellular processes. The regulation of chloroplast thioredoxins and their targets is critical for maintaining optimal photosynthetic efficiency and adapting to changing environmental conditions.
Adenosine monophosphate (AMP) is a nucleotide that is the monophosphate ester of adenosine, consisting of the nitrogenous base adenine attached to the 1' carbon atom of ribose via a β-N9-glycosidic bond, which in turn is esterified to a phosphate group. It is an important molecule in biological systems as it plays a key role in cellular energy transfer and storage, serving as a precursor to other nucleotides such as ADP and ATP. AMP is also involved in various signaling pathways and can act as a neurotransmitter in the central nervous system.