Phosphofructokinase
Encyclopedia
Phosphofructokinase-1 is the most important regulatory enzyme
of glycolysis
. It is an allosteric enzyme made of 4 subunits and controlled by many activator
s and inhibitor
s. PFK-1 catalyzes the important "committed" step of glycolysis
, the conversion of fructose 6-phosphate
and ATP
to fructose 1,6-bisphosphate and ADP
.
(M), liver
(L), and platelet
(P). The composition of the PFK1 tetramer
differs according to the tissue type it is present in. For example, mature muscle expresses only the M isozyme
, therefore, the muscle PFK1 is composed solely of homotetramers of M4. The liver and kidneys express predominantly the L isoform. Erythrocytes express both M and L subunits which randomly tetramerize to form M4, L4 and the three hybrid forms of the enzyme (ML3, M2L2, M3L). As a result, the kinetic and regulatory properties of the various isoenzymes pools are dependent on subunit composition. Tissue-specific changes in PFK activity and isoenzymic content contribute significantly to the diversities of glycolytic
and gluconeogenic
rates which have been observed for different tissues.
PFK1 is an allosteric enzyme and has a structure similar to that of hemoglobin
insofar as it is a dimer of a dimer. One half of each dimer contains the ATP binding site whereas the other half the substrate (fructose-6-phosphate or (F6P)) binding site as well as a separate allosteric binding site.
of allosterism whereby there is a concerted transition from an enzymatically inactive T-state to the active R-state. F6P binds with a high affinity to the R state but not the T state enzyme. For every molecule of F6P that binds to PFK1, the enzyme progressively shifts from T state to the R state. Thus a graph plotting PFK1 activity against increasing F6P concentrations would adopt the sigmoidal
curve shape traditionally associated with allosteric enzymes.
PFK1 belongs to the family of phosphotransferases and it catalyzes the transfer of γ-phosphate from ATP to fructose-6-phosphate. The PFK1 active site
comprises both the ATP-Mg2+ and the F6P binding sites. Some proposed residues involved with substrate binding in E. coli FPK1 include Asp127
and Arg171
. In B. stearothermophilus
PFK1, the positively charged side chain of Arg162 residue forms a hydrogen-bonded salt bridge with the negatively charged phosphate group of F6P, an interaction which stabilizes the R state relative to the T state and is partly responsible for the homotropic effect
of F6P binding. In the T state, enzyme conformation shifts slightly such that the space previously taken up by the Arg162 is replaced with Glu161
. This swap in positions between adjacent amino acid residues inhibits the ability of F6P to bind the enzyme.
Allosteric activators such as AMP
and ADP
bind to the allosteric site as to facilitate the formation of the R state by inducing structural changes in the enzyme. Similarly, inhibitors such as ATP and PEP bind to the same allosteric site and facilitate the formation of the T state, thereby inhibiting enzyme activity.
under physiological condition
s, but also because it is the committed step - the first irreversible reaction unique to the glycolytic pathway. This leads to a precise control of glucose and the other monosaccharide
s galactose
and fructose
going down the glycolysis pathway. Before this enzyme's reaction, glucose-6-phosphate
can potentially travel down the pentose phosphate pathway
, or be converted to glucose-1-phosphate for glycogenesis
PFK1 is allosterically inhibited by high levels of ATP
but AMP reverses the inhibitory action of ATP. Therefore, the activity of the enzyme increases when the cellular ATP/AMP ratio is lowered. Glycolysis is thus stimulated when energy charge falls. PFK1 has two sites with different affinities for ATP which is both a substrate
and an inhibitor.
PFK1 is also inhibited by low pH levels which augment the inhibitory effect of ATP. The pH falls when muscle is functioning anaerobically
and producing excessive quantities of lactic acid
. This inhibitory effect serves to protect the muscle from damage that would result from the accumulation of too much acid.
Finally, PFK1 is allosterically inhibited by both PEP and citrate. Phosphoenolpyruvic acid is a product further downstream the glycolytic
pathway and citrate is an early intermediate in the citric acid cycle
. Citrate buildup is a sign of the citric acid cycle
reaching saturation and thus glycolysis
slows down as there is no longer any need to commit more glucose to degradation.
PFK1 is allosterically activated by a high concentration of AMP
, but the most potent activator is fructose 2,6-bisphosphate
, which is also produced from fructose-6-phosphate by PFK2
. Hence, an abundance of F6P results in a higher concentration of fructose 2,6-bisphosphate
(F-2,6-BP). The binding of F-2,6-BP increases the affinity of PFK1 for F6P and diminishes the inhibitory effect of ATP. This is an example of feedforward stimulation as glycolysis is accelerated when glucose is abundant.
PFK is inhibited by glucagon
through repression of synthesis. Glucagon activates protein kinase A which, in turn, shuts off the kinase activity of PFK2
. This reverses any synthesis of F-2,6-BP from F6P and thus inhibits PFK1 activity.
The precise regulation of PFK1 prevents glycolysis
and gluconeogenesis
from occurring simultaneously. However, there is substrate cycling between F6P and F-1,6-BP. Fructose-1,6-bisphosphatase (FBPase) catalyzes the hydrolysis of F-1,6-BP back to F6P, the reverse reaction catalyzed by PFK1. There is a small amount of FBPase activity during glycolysis and some PFK1 activity during gluconeogenesis. This cycle allows for the amplification of metabolic signals as wells as the generation of heat by ATP hydrolysis.
gene results in Tarui's disease
, a glycogen storage disease where the ability of certain cell types to utilize carbohydrates as a source of energy is impaired.
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
of glycolysis
Glycolysis
Glycolysis is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+...
. It is an allosteric enzyme made of 4 subunits and controlled by many activator
Activator
Activator may mean:* Activator , a DNA-binding protein that regulates one or more genes by increasing the rate of transcription* Activator , a type of effector that increases the rate of enzyme mediated reactions...
s and inhibitor
Enzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
s. PFK-1 catalyzes the important "committed" step of glycolysis
Glycolysis
Glycolysis is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+...
, the conversion of fructose 6-phosphate
Fructose 6-phosphate
Fructose 6-phosphate is fructose sugar phosphorylated on carbon 6 . The β-D-form of this compound is very common in cells. The vast majority of glucose and fructose entering a cell will become converted to this at some point...
and ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
to fructose 1,6-bisphosphate and ADP
Adenosine diphosphate
Adenosine diphosphate, abbreviated ADP, is a nucleoside diphosphate. It is an ester of pyrophosphoric acid with the nucleoside adenosine. ADP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase adenine....
.
Structure
Mammalian PFK1 is a 340kd tetramer composed of three types of subunit: muscleMuscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
(M), liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
(L), and platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
(P). The composition of the PFK1 tetramer
Tetramer
A tetramer is a protein with four subunits . There are homotetramers such as glutathione S-transferase or single-strand binding protein, dimers of hetero-dimers such as hemoglobin , and heterotetramers, where each subunit is different.-Subunit interactions in tetramers:The interactions between...
differs according to the tissue type it is present in. For example, mature muscle expresses only the M isozyme
Isozyme
Isozymes are enzymes that differ in amino acid sequence but catalyze the same chemical reaction. These enzymes usually display different kinetic parameters Isozymes (also known as isoenzymes) are enzymes that differ in amino acid sequence but catalyze the same chemical reaction. These enzymes...
, therefore, the muscle PFK1 is composed solely of homotetramers of M4. The liver and kidneys express predominantly the L isoform. Erythrocytes express both M and L subunits which randomly tetramerize to form M4, L4 and the three hybrid forms of the enzyme (ML3, M2L2, M3L). As a result, the kinetic and regulatory properties of the various isoenzymes pools are dependent on subunit composition. Tissue-specific changes in PFK activity and isoenzymic content contribute significantly to the diversities of glycolytic
Glycolysis
Glycolysis is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+...
and gluconeogenic
Gluconeogenesis
Gluconeogenesis is a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids....
rates which have been observed for different tissues.
PFK1 is an allosteric enzyme and has a structure similar to that of hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
insofar as it is a dimer of a dimer. One half of each dimer contains the ATP binding site whereas the other half the substrate (fructose-6-phosphate or (F6P)) binding site as well as a separate allosteric binding site.
Mechanism
PFK1 is an allosteric enzyme whose activity can be described using the symmetry modelMWC model
In biochemistry, the MWC model describes allosteric transitions of proteins made up of identical subunits. It was proposed by Jean-Pierre Changeux based on his PhD experiments, and described by Jacques Monod, Jeffries Wyman, and Jean-Pierre Changeux...
of allosterism whereby there is a concerted transition from an enzymatically inactive T-state to the active R-state. F6P binds with a high affinity to the R state but not the T state enzyme. For every molecule of F6P that binds to PFK1, the enzyme progressively shifts from T state to the R state. Thus a graph plotting PFK1 activity against increasing F6P concentrations would adopt the sigmoidal
Sigmoid function
Many natural processes, including those of complex system learning curves, exhibit a progression from small beginnings that accelerates and approaches a climax over time. When a detailed description is lacking, a sigmoid function is often used. A sigmoid curve is produced by a mathematical...
curve shape traditionally associated with allosteric enzymes.
PFK1 belongs to the family of phosphotransferases and it catalyzes the transfer of γ-phosphate from ATP to fructose-6-phosphate. The PFK1 active site
Active site
In biology the active site is part of an enzyme where substrates bind and undergo a chemical reaction. The majority of enzymes are proteins but RNA enzymes called ribozymes also exist. The active site of an enzyme is usually found in a cleft or pocket that is lined by amino acid residues that...
comprises both the ATP-Mg2+ and the F6P binding sites. Some proposed residues involved with substrate binding in E. coli FPK1 include Asp127
Aspartic acid
Aspartic acid is an α-amino acid with the chemical formula HOOCCHCH2COOH. The carboxylate anion, salt, or ester of aspartic acid is known as aspartate. The L-isomer of aspartate is one of the 20 proteinogenic amino acids, i.e., the building blocks of proteins...
and Arg171
Arginine
Arginine is an α-amino acid. The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that codify for arginine during...
. In B. stearothermophilus
Bacillus stearothermophilus
Bacillus stearothermophilus is a rod-shaped, Gram-positive bacterium and a member of the division Firmicutes. The bacteria is a thermophile and is widely distributed in soil, hot springs, ocean sediment, and is a cause of spoilage in food products. It will grow within a temperature range of 30-75...
PFK1, the positively charged side chain of Arg162 residue forms a hydrogen-bonded salt bridge with the negatively charged phosphate group of F6P, an interaction which stabilizes the R state relative to the T state and is partly responsible for the homotropic effect
Allosteric regulation
In biochemistry, allosteric regulation is the regulation of an enzyme or other protein by binding an effector molecule at the protein's allosteric site . Effectors that enhance the protein's activity are referred to as allosteric activators, whereas those that decrease the protein's activity are...
of F6P binding. In the T state, enzyme conformation shifts slightly such that the space previously taken up by the Arg162 is replaced with Glu161
Glutamic acid
Glutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...
. This swap in positions between adjacent amino acid residues inhibits the ability of F6P to bind the enzyme.
Allosteric activators such as AMP
Adenosine monophosphate
Adenosine monophosphate , also known as 5'-adenylic acid, is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid and the nucleoside adenosine. AMP consists of a phosphate group, the sugar ribose, and the nucleobase adenine...
and ADP
Adenosine diphosphate
Adenosine diphosphate, abbreviated ADP, is a nucleoside diphosphate. It is an ester of pyrophosphoric acid with the nucleoside adenosine. ADP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase adenine....
bind to the allosteric site as to facilitate the formation of the R state by inducing structural changes in the enzyme. Similarly, inhibitors such as ATP and PEP bind to the same allosteric site and facilitate the formation of the T state, thereby inhibiting enzyme activity.
Regulation
PFK1 is the most important control site in the mammalian glycolytic pathway. This step is subject to extensive regulation since it is not only highly endergonicEndergonic
Endergonic means "absorbing energy in the form of work." Endergonic reactions are not spontaneous...
under physiological condition
Physiological condition
Physiological condition or, more often "physiological conditions" is a term used in biology, biochemistry, and medicine. It refers to conditions of the external or internal milieu that may occur in nature for that organism or cell system, in contrast to artificial laboratory conditions...
s, but also because it is the committed step - the first irreversible reaction unique to the glycolytic pathway. This leads to a precise control of glucose and the other monosaccharide
Monosaccharide
Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...
s galactose
Galactose
Galactose , sometimes abbreviated Gal, is a type of sugar that is less sweet than glucose. It is a C-4 epimer of glucose....
and fructose
Fructose
Fructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...
going down the glycolysis pathway. Before this enzyme's reaction, glucose-6-phosphate
Glucose-6-phosphate
Glucose 6-phosphate is glucose sugar phosphorylated on carbon 6. This compound is very common in cells as the vast majority of glucose entering a cell will become phosphorylated in this way....
can potentially travel down the pentose phosphate pathway
Pentose phosphate pathway
The pentose phosphate pathway is a process that generates NADPH and pentoses . There are two distinct phases in the pathway. The first is the oxidative phase, in which NADPH is generated, and the second is the non-oxidative synthesis of 5-carbon sugars...
, or be converted to glucose-1-phosphate for glycogenesis
Glycogenesis
Glycogenesis is the process of glycogen synthesis, in which glucose molecules are added to chains of glycogen for storage. This process is activated during rest periods following the Cori cycle, in the liver, and also activated by insulin in response to high glucose levels, for example after a...
PFK1 is allosterically inhibited by high levels of ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
but AMP reverses the inhibitory action of ATP. Therefore, the activity of the enzyme increases when the cellular ATP/AMP ratio is lowered. Glycolysis is thus stimulated when energy charge falls. PFK1 has two sites with different affinities for ATP which is both a substrate
Substrate (biochemistry)
In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...
and an inhibitor.
PFK1 is also inhibited by low pH levels which augment the inhibitory effect of ATP. The pH falls when muscle is functioning anaerobically
Anaerobic respiration
Anaerobic respiration is a form of respiration using electron acceptors other than oxygen. Although oxygen is not used as the final electron acceptor, the process still uses a respiratory electron transport chain; it is respiration without oxygen...
and producing excessive quantities of lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
. This inhibitory effect serves to protect the muscle from damage that would result from the accumulation of too much acid.
Finally, PFK1 is allosterically inhibited by both PEP and citrate. Phosphoenolpyruvic acid is a product further downstream the glycolytic
Glycolysis
Glycolysis is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+...
pathway and citrate is an early intermediate in the citric acid cycle
Citric acid cycle
The citric acid cycle — also known as the tricarboxylic acid cycle , the Krebs cycle, or the Szent-Györgyi-Krebs cycle — is a series of chemical reactions which is used by all aerobic living organisms to generate energy through the oxidization of acetate derived from carbohydrates, fats and...
. Citrate buildup is a sign of the citric acid cycle
Citric acid cycle
The citric acid cycle — also known as the tricarboxylic acid cycle , the Krebs cycle, or the Szent-Györgyi-Krebs cycle — is a series of chemical reactions which is used by all aerobic living organisms to generate energy through the oxidization of acetate derived from carbohydrates, fats and...
reaching saturation and thus glycolysis
Glycolysis
Glycolysis is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+...
slows down as there is no longer any need to commit more glucose to degradation.
PFK1 is allosterically activated by a high concentration of AMP
Adenosine monophosphate
Adenosine monophosphate , also known as 5'-adenylic acid, is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid and the nucleoside adenosine. AMP consists of a phosphate group, the sugar ribose, and the nucleobase adenine...
, but the most potent activator is fructose 2,6-bisphosphate
Fructose 2,6-bisphosphate
Fructose 2,6-bisphosphate abbreviated Fru-2,6-P2, is a metabolite that allosterically affects the activity of the enzymes phosphofructokinase 1 and fructose 1,6-bisphosphatase to regulate glycolysis and gluconeogenesis...
, which is also produced from fructose-6-phosphate by PFK2
PFK2
Phosphofructokinase 2 or fructose biphosphatase 2 , is an enzyme responsible for regulating the rates of glycolysis and gluconeogenesis in the human body. It is a homodimer of 55 kDa subunits arranged in a head-to-head fashion, with each polypeptide chain consisting of independent kinase and...
. Hence, an abundance of F6P results in a higher concentration of fructose 2,6-bisphosphate
Fructose 2,6-bisphosphate
Fructose 2,6-bisphosphate abbreviated Fru-2,6-P2, is a metabolite that allosterically affects the activity of the enzymes phosphofructokinase 1 and fructose 1,6-bisphosphatase to regulate glycolysis and gluconeogenesis...
(F-2,6-BP). The binding of F-2,6-BP increases the affinity of PFK1 for F6P and diminishes the inhibitory effect of ATP. This is an example of feedforward stimulation as glycolysis is accelerated when glucose is abundant.
PFK is inhibited by glucagon
Glucagon
Glucagon, a hormone secreted by the pancreas, raises blood glucose levels. Its effect is opposite that of insulin, which lowers blood glucose levels. The pancreas releases glucagon when blood sugar levels fall too low. Glucagon causes the liver to convert stored glycogen into glucose, which is...
through repression of synthesis. Glucagon activates protein kinase A which, in turn, shuts off the kinase activity of PFK2
PFK2
Phosphofructokinase 2 or fructose biphosphatase 2 , is an enzyme responsible for regulating the rates of glycolysis and gluconeogenesis in the human body. It is a homodimer of 55 kDa subunits arranged in a head-to-head fashion, with each polypeptide chain consisting of independent kinase and...
. This reverses any synthesis of F-2,6-BP from F6P and thus inhibits PFK1 activity.
The precise regulation of PFK1 prevents glycolysis
Glycolysis
Glycolysis is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+...
and gluconeogenesis
Gluconeogenesis
Gluconeogenesis is a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids....
from occurring simultaneously. However, there is substrate cycling between F6P and F-1,6-BP. Fructose-1,6-bisphosphatase (FBPase) catalyzes the hydrolysis of F-1,6-BP back to F6P, the reverse reaction catalyzed by PFK1. There is a small amount of FBPase activity during glycolysis and some PFK1 activity during gluconeogenesis. This cycle allows for the amplification of metabolic signals as wells as the generation of heat by ATP hydrolysis.
Genes
There are three phosphofructokinase genes in humans:- PFKLPFKL6-phosphofructokinase, liver type is an enzyme that in humans is encoded by the PFKL gene.-Further reading:...
- liverLiverThe liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion... - PFKMPFKM6-phosphofructokinase, muscle type is an enzyme that in humans is encoded by the PFKM gene.-Further reading:...
- muscleMuscleMuscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to... - PFKPPFKPPhosphofructokinase, platelet, also known as PFKP is an enzyme which in humans is encoded by the PFKP gene.- Function :The PFKP gene encodes the platelet isoform of phosphofructokinase...
- plateletPlateletPlatelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
Disease
A genetic mutation in the PFKMPFKM
6-phosphofructokinase, muscle type is an enzyme that in humans is encoded by the PFKM gene.-Further reading:...
gene results in Tarui's disease
Phosphofructokinase Deficiency
Phosphofructokinase deficiency, also known as Glycogen storage disease type VII or Tarui's disease, is metabolic disorder with autosomal recessive inheritance.It may affect humans as well as other mammals...
, a glycogen storage disease where the ability of certain cell types to utilize carbohydrates as a source of energy is impaired.
See also
- PFK2PFK2Phosphofructokinase 2 or fructose biphosphatase 2 , is an enzyme responsible for regulating the rates of glycolysis and gluconeogenesis in the human body. It is a homodimer of 55 kDa subunits arranged in a head-to-head fashion, with each polypeptide chain consisting of independent kinase and...
(converts fructose 6-phosphate to fructose 2,6-bisphosphate through on site, or the opposite, on another site) - PFPPFP (enzyme)Diphosphate—fructose-6-phosphate 1-phosphotransferase also known as PFP is an enzyme of carbohydrate metabolism in plants and some bacteria...
(reversibly interconverts fructose 6-phosphate and fructose 1,6-bisphosphate using inorganic pyrophosphatePyrophosphateIn chemistry, the anion, the salts, and the esters of pyrophosphoric acid are called pyrophosphates. Any salt or ester containing two phosphate groups is called a diphosphate. As a food additive, diphosphates are known as E450.- Chemistry :...
rather than ATP) - fructose bisphosphataseFructose bisphosphataseFructose bisphosphatase is an enzyme in the liver that converts fructose-1,6-bisphosphate to fructose 6-phosphate in gluconeogenesis . Fructose bisphosphatase catalyses the reverse of the reaction which is catalysed by phosphofructokinase, which is involved in the process of glycolysis...
(hydrolyses fructose 1,6-bisphosphate to fructose 6-phosphate)