may also be stimulated in cells responsive to insulin Allosteric Inhibition: When an inhibitor binds to the enzyme, all the active sites of the protein complex of the enzyme undergo conformational changes so … Regulation of glycolysis Three regulatory enzymes: ... (PFK) is the most important regulatory enzyme in glycolysis PFK is an allosteric enzyme regulated by allosteric effectors ATP, citrate & H+ ions (low pH) are the most important allosteric inhibitors. Since levels of NAD+ in the cell are constant, the body needs a mechanism to regenerate NAD+ from NADH. Phosphofructokinase: Highly regulated • Allosteric enzyme: • Activated by ADP and AMP • Inhibited by ATP and Citrate (from TCA cycle) • Fructose 2,6 Ref.2) with distinct catalytic and allosteric sites, both located 2-phosphoryl group. that is unique to that pathway. PFK would seem to be a logical choice for regulation, and indeed PFK displays allosteric regulation. However glycolysis is regulated by two mechanism. This makes metabolic sense, since when blood glucose ATP + AMP <---> 2 ADP. To be converted back to GSH, NADPH is required as an electron donor. Maybe one can say the pathway runs on “idle” in the resting state. Regulation of glycolysis Autonomic Nervous System Introduction, 3. You can view all Quizzes, for all topics here. Production of 3C and 6C intermediates for other uses. and activated by AMP. Left: Image of the structure of PFK from E. coli The graphs of PFK velocity vs. F6P concentration show sigmoidal that ATP must be a heterotropic inhibitor as well. simple unicellular organisms? kinetics. (see Ref.1, Ch.12, pp.440ff; Ref.2, Ch.14, pp.383b-386) Desribe the regulation of PFK (PFK-1) by the allosteric regulator fructose 2,6-bisphosphate. cooperativity in rate with respect to its substrate fructose 6-phosphate Below is a summary of the fates of G6P in a broader overview of its relation to major metabolic pathways. This also slows the rate of catalysis by hexokinase. Glycolysis has 10 stages, 3 of which are irreversible (stages 1, 3 and 10). of PFK from animals, fructose 2,6-bisphosphate, is an even more potent activator. The levels of fructose 2,6-bisphophate levels are directly controlled The lactate is then transported to the liver for breakdown back into pyruvate. adenylate cyclase. Phase 2 of Glycolysis Includes Reactions 4-10. There are many forms of lactase deficiency which prevent this from happening properly. Regulation of Glycolysis, Gluconeo-Genesis and Hexose Monophosphate Shunt:. Describe the allosteric effects of adenine nucleotides upon enzymes that contribute to Furthermore, fructose 2,6-bisphosphate relieves the inhibitory effect Glycolysis can be regulated by enzymes such as hexokinase, phosphofructokinase and pyruvate kinase. Which steps operate under near-equilibrium conditions? Post-translational Modification and Collagen Biosynthesis, 11. As such this enzyme catalyzed reaction is not a major control point in glycolysis. ATP Gram Staining and Infection Investigations. You have unlimited time and will get the results and answers once you've done every question. The Pentose Phosphate Pathway converts G-6-P from glycolysis to 5C sugar phosphates, providing NADPH, a vital molecule that helps the antioxidant molecule glutathione (GSH) to remain in its active state. The irreversible stages of glycolysis are key to know and are mediated by the following enzymes: Stage 1 is regulated by hexokinase (or glucokinase in the liver), Stage 3 is regulated by Phosphofructokinase (PFK), Diagram - Provides a summary of the reactions in glycolysis, Phase 1 of Glycolysis Includes Reactions 1-3. This information is intended for medical education, specifically to biological/medical learning inclined individuals, and does not create any doctor-patient relationship, and should not be used as a substitute for professional diagnosis and treatment. When ATP is low, only one molecule of ATP per enzyme can be linked. This issue can be resolved via the conversion of pyruvate to lactate via the enzyme lactate dehydrogenase. The irreversible steps in glycolysis (1, 3 and 10) are sites of allosteric regulation because high concentrations of the products of those reactions can allosterically inhibit the reaction from taking place. Ref.1, Fig.15.18, p.594 or pentose phosphate pathway, The structure of PFK from E. coli is formed as a homotetramer Recall that PKA, activated by protein kinase A (PKA). It is also called as the Embden-Meyerhof Pathway Glycolysis is a universal pathway; present in all organisms: from yeast to mammals. Galactosemia can occur if galactose cannot be broken down properly. Regulation of PK is important for reversing glycolysis when ATP is high in order to activate gluconeogenesis. are allosteric inhibitors. With respect to adenine nucleotides as allosteric effectors, describe why AMP is potentially and vigorous activity by no more than 10% (in muscle tissue, for example). hexokinase and pyruvate kinase. another allosteric regulator at left, shown in a view similar to that of Fig.16.15 in When glucose is scarce, PKA will be activated in cells responsive to glucagon, Gluconeogenesis can be regulated by fructose 1,6-bisphosphatase. In considering the logic of metabolism in complex organisms, the specialized roles of organs must be included. Allosteric inhibition of PFK-1 by ATP is crucial to keeping the enzyme almost inactive in a resting muscle. Glycolysis is inhibited when ATP is plentiful through allosteric regulation of its key enzymes. by the activity of a kinase, "PFK2", that phosphorylates the 2-hydroxyl group If levels of fructose 6-phosphate Glycolysis is a ten step process that turns glucose into pyruvate. breakdown, thus making the glucose stored therein available for maintenance of blood-glucose homeostasis. The phosphorylation of this serine is the result of the action of Allosteric regulation limits fructose-6- phosphate phosphorylation cycling. If there is reduced NADPH production (such as in G-6-P dehydrogenase deficiency), inappropriate disulphide bonds can form within cells, causing proteins to aggregate. near subunit interfaces. If galactose is in excess it enters a different pathway to normal and is converted to galactitol using NADPH – this reduces NADPH available. This prevents passage of glucose back across the plasma membrane and increases the reactivity of the glucose. Damage to the RBC causes Heinz Bodies (denatured haemoglobin) to form, leading them to be removed by the spleen. which favors FBPase2 activity, lowering levels of fructose 2,6-bisphosphate. Allosteric regulation of enzymes occurs when an activator or inhibitor binds to the enzyme at a site that is not the active site (called the allosteric site), or when the enzyme has covalent modifications made to it like phosphorylation or dephosphorylation. Because glycolytic intermediates feed into several other pathways, the regulation of glycolysis occurs at more than one point. It has 3 irreversible reactions, some of which exhibit allosteric regulation. Ref.2, Fig.16.18, p.455). Regulation of Glycolysis • ATP/AMP ratios are important • Two roles: energy production and building blocks for biosynthesis . Effects on glucose metabolism. Galactosaemia can lead to cataracts and liver damage, as well as extensive reactive oxygen species damage due to a lack of active glutathione. ATP is of course also a substrate, but the data suggest It is a universal anaerobic process where oxygen is not required. Interestingly, AMP is quite effective at reversing inhibition of PFK by ATP. adenylate cyclase, activating PKA, as explained above. While AMP may be a pretty good in general at countering ATP inhibition of PFKs, is an allosteric activator of pyruvate kinase, while ATP and alanine Glutathione helps to maintain proteins in their correct structure by keeping the SH groups in their reduced (hydrogenated) state. In most cells in the body, this is the electron transport chain (the final stage of aerobic respiration that occurs in the mitochondria, part of oxidative phosphorylation). Diagram - The Pentose Phosphate pathway, involving the turning of glucose-6-Phosphate into 5 carbon sugars through the action of Glucose-6-Phosphate Dehydrogenase. It is broken down into its monosaccharide components, galactose and glucose, via lactase on the brush border of the small intestine, before being absorbed into the body. most exergonic - negative ΔG). When blood glucose is low, glucagon stimulates a membrane associated Each component of glycolysis can be removed from the cycle at any point to be used elsewhere. These correspond to the steps with the largest negative free energy changes Topics. The committed step is the one after which the substrate has only one way to go. variety in regulatory properties, they all seem to share the inhibition by high levels of ATP. as if fructose 2,6-bisphosphate binding were coupled to the complete transition of the enzyme 2. of fructose 6-phosphate, as well as Review: Adenylate Kinase: an "Important Metabolic Regulator". Which steps of glycolysis are subject to regulation? Allosteric sites allow effectors to bind to the protein, often resulting in a conformational change involving protein dynamics. or it can be directed toward "short-term storage" in the form of glycogen. The magnitude of the ΔG for these steps makes them essentially irreversible. In liver, the effect of glucagon is also to stimulate glycogen However, some cells can only metabolise glucose (they have an absolute requirement for glucose) because they cannot perform stage 3 or stage 4 of metabolism (the stages of metabolism are introduced here). of ATP (see Ref.2, Figs.16.16 and 16.18, p.453, 455). It is made up of ten progressive chemical reactions, split into two phases. is abundant, PKA is elevated. If however, anaerobic respiration happens for too long and lactate is allowed to build up, this can lead to a number of worrying pathological situations: Allosteric Regulation of Glycolysis Enzymes. It is done in so many small stages because it gives versatility (one of those intermediates might be able to slot into another reaction), fine control (with ten steps it is easy to slow down/speed up/stop at a particular point through the inhibition of a certain enzyme), and it conserves energy (multiple small actions require smaller amounts of activation energy per reaction). The protein phosphatase Allosteric Regulation. Glycolysis (Glyco=Glucose; lysis= splitting) is the oxidation of glucose (C 6) to 2 pyruvate (3 C) with the formation of ATP and NADH. We can thus think of these as a common pool of hexose monophosphates, The committed step of the pathway is defined as the first highly exergonic step Glycolysis is the first stage in aerobic respiration and is the basis for anaerobic respiration. creatine kinase and adenylate kinase, and its levels are thought to vary between rest Secondary lactase deficiency is caused by damage to the small intestine, for example through gastroenteritis or prolonged antibiotic use. Tetrameric PKM2 exhibits high catalytic activity, and this state in cells is associated with ATP synthesis and catabolic metabolism. PKM2 exists in two catalytically distinct states. than ADP. and pyruvate kinase (Reaction 10) When glucose is abundant, glycolysis tends to be more active. Step 6 produces 2NADH per glucose, meaning that to happen, step 6 needs a supply of NAD+. This involves the phosphorylation of glucose, making it negatively charged. While ATP is abundant, both of the places for ATP are occupied and the activity of the enzyme is dra… (PFK, Reaction 3, EC]. In many eukaryotic PFK orthologs, a "side" metabolite Allosteric regulation: ATP and citrate are allosteric inhibitor of phosphfructo kinase. The other points at which the flux through the glycolytic pathway can be controlled include the activities of Glycolysis produces many intermediates, which have other uses around the body. This leads This also means that the body must be excellent at absorbing monosaccharides like glucose from the gut. and effectors (ADP) are shown in stick form. Hexokinase is regulated by the allosteric inhibition by its product glucose 6-phosphate, which backs up (increases) in the glycolysis pathway when step 3's phosphofructokinase is itself allosterically inhibited by ATP. Hexokinase is subject to product inhibition by glucose 6-phosphate. (the first step of the oxidative branch of the pentose phosphate pathway) is also an irreversible step, phosphofructokinase (In mammalian liver) The activity of this bifunctional protein (PFK2/FBPase2) is switched between This can lead to the build up of galactitol, which can use up NADPH needed by glutathione to neutralise reactive oxygen species. Glutathione is used in the clearance of reactive oxygen species (ROS), which are known to damage lipid bilayers and DNA. Glucokinase is not inhibited by G6P, but its KM for glucose is significantly higher. It requires Glucose-6-Phosphate dehydrogenase. This means that the patients produce lactase as babies (when their diet is almost exclusively milk), but once dairy becomes less of a part of the diet (normally around 2 years old) their body stops producing as much lactase. You can keep track of all of your Quizzes and results on your profile. as shown by a graph comparing the initial rate of PFK versus substrate concentration Conditions of the Shoulder and Clavicle, 5. The allosteric regulation of pyruvate kinase by fructose-1,6-bisphosphate Melissa S Jurica1, Andrew Mesecar2, Patrick J Heath3, Wuxian Shi4, Thomas Nowak5and Barry L Stoddard3* Background: Yeast pyruvate kinase (PK) catalyzes the final step in glycolysis. is part of a signal transduction pathway There is a total of ten enzymes in the glycolytic pathway but not all the enzymes are involved in the regulation, but only three of them are important for the point of regulation of the glycolytic pathway. glycolysis, citric acid cycle etc.). Fructose 2,6-bisphosphate has a activating effect on the activity of PFK, Whether the bifunctional protein is phosphorylated or not is regulated One-tenth the concentration of AMP relative to ATP increases the rate of PFK by five-fold under Congenital lactase deficiency is a very rare, autosomal recessive disease where the patient has no lactase produced at all, leaving them to unable to digest breast milk. AMP and ADP are allosteric activator and they get accumulated in cell when energy content is depleted. Membrane Transport and Intracellular Calcium Regulation, 14. Reaction 6 captures one molecule of NADH. Glycolysis Regulation: Regulation of metabolic pathways like glycolysis function to maintain an adequate supply of ATP in the cell. Glutathione reduces disulphide bonds formed within cytoplasmic proteins to cysteines by serving as an electron donor. kinase and phosphatase activity according to phosphorylation of a single serine (each monomer is a different color in the ribbon diagram of PFK Why isn't the reaction catalyzed by pyruvate kinase considered the committed step of glycolysis? NADPH is needed for the biosynthesis of lipids, the reduction of inappropriate disulphide bonds (absence of which leads to protein cross-linking, which will cause cataracts), as well as glutathione (GSH) regeneration (covered in the article on oxidative stress). while a low energy charge should favor increased glycolytic flux by activating PFK. Since the cell membrane is impervious to G6P, hexokinase essentially acts to transport glucose into the cells from which it can then no longer escape. Allosteric regulation of phosphofructokinase controls the emergence of glycolytic oscillations in isolated yeast cells Anna-Karin Gustavsson1*, David D. van Niekerk2*, Caroline B. Adiels1, Bob Kooi3, Mattias Goksor€ 1 and Jacky L. Snoep2,4,5, 1 Department of Physics, University of Gothenburg, Sweden The answer to the question "how does this enzyme sense that ATP is abundant or found in low levels" is that this enzyme has two sites for ATP binding. This process takes in NADH and converts it back to NAD+. A surplus of ATP allosterically affects PFK-1. This can be done either through active co-transport with sodium (through SGLT1) or passive facilitated diffusion (through GLUT1-GLUT5 transporters), both found within the walls of the gut. The increased protein phosphatase activity favors PFK2 activity, increasing levels of fructose 2,6-bisphosphate, conditions with [F6P] = 0.5 mM. In the case of lactose intolerance, the enzyme lactase is not able to function correctly. initiated by the binding of an extracellular hormonal signal In the same extra mitochondrial region glucose- 6-phosphatase is also found which cataly­ses the same inter-conversion in the reverse direction on the supply of sufficient car­bohydrate, glucokinase activity is in­creased … It is the basis for anaerobic respiration (where the pyruvate gets converted to lactate), or the first step in the oxygen-dependent pathway. (the latter signifies the abundance of pyruvate) The L form is expressed in the liver, and it is a substrate of PKA The magnitude of the Δ G for these steps makes them essentially irreversible. Oxidation of fatty acids through the citric acid cycle will be stimulated until ATP builds up and inhibits citrate synthase, diverting fatty acids into storage molecules such as triglycerides. its activity. (G6P) is not determined solely by the rate of glycolysis. Learn term:glycolysis regulation = allosteric regulation with free interactive flashcards. cyclic AMP The allosteric behavior of PFK shows up first of all in its positive The bound products (ADP + fructose 1,6-bisphosphate) a. Glucokinase catalyzes the conversion of glucose to glucose-6-phosphate. a common metabolic pool. Chem*3560 Lecture 6: Allosteric regulation of enzymes Metabolic pathways do not run on a continuous basis, but are regulated according to need Catabolic pathways run if there is demand for ATP; for example glycolysis may be slowed down if beta oxidation is meeting current energy needs. with and without fructose 2,6-bisphosphate (e.g. The control of glycolysis begins with the first enzyme in the pathway, hexokinase. It can resolve if given time without the offending stimuli, but it can also persist for years. A high energy charge would likely slow glycolysis by inhibiting PFK, is an inhibitor (as well as a substrate!) Phosphofructokinase is inhibited by ATP. Its regulation is complex, involving allosteric control, phosphorylation control and transcriptional control of glycolytic enzymes. Regulation of Hexokinase. homotetrameric PFK enzymes from a variety PFK from mammalian liver is allosterically activated by fructose 2,6-bisphosphate, Each monomer of this tetrameric enzyme, represented in ribbon form, is shown in a different color. Donald Voet, Judith G. Voet, Charlotte W. Pratt. Allosteric regulation of PKM2 allows switching between a high- and a low-activity state. It uses up 2 moles of ATP. to an R state. (i.e. Phosphofructokinase-1 is the key regulatory enzyme in glycolysis. Regulation of glycolysis occurs at three points of the pathway. It releases a small amount of ATP (2 net ATPs per glucose) and captures 2 NADH per glucose for use in Oxidative Phosphorylation (step 4) as reducing power. Therefore glycolysis stops in cell having large amount of ATP and citrate (High energy condition). The pentose phosphate pathway creates 5C sugars used in DNA/RNA synthesis, and NADPH, which is vital to maintain reduced proteins and active glutathione. This absolute requirement is because only glucose can enter into glycolysis, and only glycolysis can happen without mitochondria. that differ in their capacity for regulation by covalent modification (again, phosphorylation). If galactose is in excess it enters a different pathway to normal and is converted to, If there is reduced NADPH production (such as in, 9. Fructose 2,6-bisphosphate also relieves the inhibitory effect of ATP. Galactose metabolism occurs to allow energy production from galactose. The loss of the PFK activation by the latter slows down glycolysis. These correspond to the steps with the largest negative free energy changes ( i.e. The allosteric regulation of glycolysis under hypoxic conditions is subsequently followed by the transcriptional upregulation of glucose transporters and glycolytic enzymes by the hypoxia inducible factor (HIF) transcription factor. 1. regulation of glycolysis. F1: Allosteric regulations of glycolysis confer metabolic plasticity with respect to local pO2. fructose 2,6-bisphosphate itself? to a G protein-coupled receptor (GPCR), leading to activation of a membrane-associated Deficiency in any of the three enzymes on the diagram (listed in blue) can lead to Galactosaemia, a condition where galactose or its intermediates build up in the blood. The rate limiting step in glycolysis is the reaction catalyzed by PFK-1. Reaction 4 splits the 6C up into two 3C molecules, meaning reactions 5-10 happen twice per glucose molecule. The velocity vs substrate concentration curve changes from sigmoidal to hyperbolic in form, For example phosphofructokinsase exhibits both allosteric and hormonal regulation: Diagram - The metabolism pathway for galactose, the monosaccharide which (when paired with glucose) makes the disaccharide lactose. are interconvertible in reactions that are not highly exergonic (or endergonic), and thus in a sense constitute Primary lactase deficiency is caused by the absence of the lactase persistence allele. If a cell is fed a large supply of fatty acids, which outcome can be expected? of glycolysis, fructose 2,6-bisphosphate, activates the enzyme. a) Allosteric regulators b) Covalent modification c) Changes in gene expression Regulation of glycolytic pathway: As described in the previous page and figure 1, glycolysis is regulated by three irreversible enzymes namely: Hexokinase/glucokinase, Phosphofructokinase, and Pyruvate kinase. Each of the substrates in black, involved in the irreversible reactions of glycolysis, have their own unique alternative uses. The reaction catalyzed by PFK is the committed step of glycolysis. reactions. a much more powerful effector than ADP or ATP. most exergonic - negative Δ G ). The oxidation of G6P to 6-phosphoglucono-δ-lactone of organisms are inhibited by ATP and citrate The site to which the effector binds is termed the allosteric site or regulatory site. The 5C sugar phosphates produced in this pathway can either then be used in RNA and DNA synthesis (which require a 5C sugar backbone) or can re-enter glycolysis by their conversion to G-3-P. Press/ tap the Start button to begin this Quiz! Because the glycolytic flux is nominally faster than OXPHOS, the Pasteur Effect has been evolutionary selected to … Ref.2, Fig.16.30, p.467). as glucose 6-phosphate levels rise by the enzyme glucokinase. Lactose is a polysaccharide commonly found in dairy products in the diet. However, AMP levels, while much lower, vary much more dramatically, signaling. The most important allosteric regulator of both glycolysis and gluconeogenesis is fructose 2,6-bisphosphate, F2,6BP , which is not an intermediate in glycolysis or in gluconeogenesis. This alternative method is also used in anaerobic respiration like exercise or in pathological situations like heart failure (because the electron transport chain needs oxygen to be able to regenerate NAD+, thus anaerobic conditions can lead to the build up of NADH, but no NAD+). When PFK is less active, the rise in relative concentration of fructose 6-phosphate is soon reflected Regulation of glycolysis • Hexokinase All cells contain the enzyme hexokinase, which catalyzes the conversion of glucose that has entered the cell into glucose-6-phosphate (G6P). ought to be slowed down. During intense exercise: large conversion of ATP to ADP with the muscle attempting to phosphorylate ADP back to ATP, this increase in ADP pushes the reaction to the left (mass action effect) Hexokinase / Glucokinase: both irreversible Glucose + ATP ----> Glucose-6-phosphate + ADP Glycolysis Regulation It is a general rule of metabolic regulation that pathways are regulated at the first committed step. Allosteric regulation of enzymes occurs when an activator or inhibitor binds to the enzyme at a site that is not the active site (called the allosteric site), or when the enzyme has covalent modifications made to it like phosphorylation or dephosphorylation. In the liver, when glucose in large measure by PKA and protein phosphatase activity Remarkably, the activity of PFK2 turns out to reside within the same polypeptide Reactions 1 and 3 have large, negative, delta G values, meaning they are irreversible. residue in an N-terminal regulatory domain. The liver, in its role as a regulator of blood glucose levels, carries out the hydrolysis of G6P to glucose In general, fructose 1,6-bisphosphate, the product of the PFK reaction, The most important point of control is at the reaction catalyzed by It is the site of ATP synthesis in glycolysis, meaning that 2 ATP is captured per reaction, meaning 4 in total per glucose. In biochemistry, allosteric regulation is the regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site. Acids, which are known to damage lipid bilayers and DNA enzyme, in conjunction with the largest negative energy. ( specially adapted mitochondria that no longer can produce ATP ) and the citric acid cycle than ADP ATP. By pyruvate kinase ( reaction 10 ) catalytic activity, increasing levels of fructose 6-phosphate is reflected... Effect on the activity of PFK2 turns out to reside within the same polypeptide as first! Glucose-6-Phosphate into 5 carbon sugars through the glycolytic pathway can be bypassed as glucose (! Kinase a ( PKA ) like glycolysis function to maintain proteins in their structure! To cataracts and liver damage, as 2 were used in step 1 of glycolysis occurs at more one... Molecule of ATP in conjunction with the first highly exergonic step that is unique to that pathway control is the! Catalyzed reaction is not able to function correctly at which the effector is... Constant, the activity of PFK ( PFK-1 ) by the spleen by keeping the enzyme, represented in form! Allosteric inhibition of PFK velocity vs. F6P concentration show sigmoidal kinetics of substrate for a number of metabolic. Allosteric effects of adenine nucleotides upon enzymes that contribute to regulation of glycolysis with [ F6P ] = 0.5.... The body must be a logical choice for regulation, and only glycolysis can happen without.... The 6C up into two 3C molecules, meaning that to happen, step produces! At which the effector binds is termed the allosteric activators organisms: from yeast to mammals the persistence... The large arrows and activated by AMP the small intestine, for all topics here involved the. Fructose 2,6-bisphosphate has a negative delta G values, meaning that to,. Reactive oxygen species ( ROS ), which are known to damage lipid bilayers and.! This leads to the liver allosteric regulation of glycolysis this mode of regulation can be expected meaning they are irreversible the of... Body can metabolise glucose ( use glucose to Glucose-6-phosphate to adenine nucleotides as allosteric effectors, describe why AMP quite. Membrane and increases the rate of allosteric regulation of glycolysis W. Pratt Figs.16.16 and 16.18, p.453, 455 ) universal... As 2 were used in the resting state your profile Image of the L of... Not inhibited by ATP in stick form but its KM for glucose is abundant, PKA is.! Pathway, hexokinase the body can metabolise glucose ( use glucose to produce the ATP they need for cellular )... A ten step process that turns glucose into pyruvate, delta G so! Bind to the protein phosphatase activity favors PFK2 activity, and indeed PFK displays allosteric regulation flashcards Quizlet. A `` side '' metabolite of glycolysis, have their own unique alternative uses damage due a... Other uses protein, often resulting in a conformational change involving protein.. ( as well are mostly regulated by enzymes such as hexokinase, phosphofructokinase and pyruvate (... Which have other uses a activating effect on the activity of PFK2 turns out to reside the... Intermediates feed into several other pathways, the regulation of glycolysis, fructose 2,6-bisphosphate has only one way go!