Gluconeogenesis

Gluconeogenesis

Overview
Gluconeogenesis is a metabolic pathway
Metabolic pathway
In biochemistry, metabolic pathways are series of chemical reactions occurring within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function...

 that results in the generation of glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 from non-carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

 carbon substrates such as lactate
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...

, glycerol
Glycerol
Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

, and glucogenic amino acid
Glucogenic amino acid
A glucogenic amino acid is an amino acid that can be converted into glucose through gluconeogenesis. This is in contrast to the ketogenic amino acids, which are converted into ketone bodies....

s.

It is one of the two main mechanisms humans and many other animals use to keep blood glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 levels from dropping too low (hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...

). The other means of maintaining blood glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 levels is through the degradation of glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...

 (glycogenolysis
Glycogenolysis
Glycogenolysis is the conversion of glycogen polymers to glucose monomers. Glycogen is catabolized by removal of a glucose monomer through cleavage with inorganic phosphate to produce glucose-1-phosphate...

).

Gluconeogenesis is a ubiquitous process, present in plants, animals, fungi, bacteria, and other microorganisms. In animals, gluconeogenesis takes place mainly in the 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...

 and, to a lesser extent, in the cortex of kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

s.
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Encyclopedia
Gluconeogenesis is a metabolic pathway
Metabolic pathway
In biochemistry, metabolic pathways are series of chemical reactions occurring within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function...

 that results in the generation of glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 from non-carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

 carbon substrates such as lactate
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...

, glycerol
Glycerol
Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

, and glucogenic amino acid
Glucogenic amino acid
A glucogenic amino acid is an amino acid that can be converted into glucose through gluconeogenesis. This is in contrast to the ketogenic amino acids, which are converted into ketone bodies....

s.

It is one of the two main mechanisms humans and many other animals use to keep blood glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 levels from dropping too low (hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...

). The other means of maintaining blood glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 levels is through the degradation of glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...

 (glycogenolysis
Glycogenolysis
Glycogenolysis is the conversion of glycogen polymers to glucose monomers. Glycogen is catabolized by removal of a glucose monomer through cleavage with inorganic phosphate to produce glucose-1-phosphate...

).

Gluconeogenesis is a ubiquitous process, present in plants, animals, fungi, bacteria, and other microorganisms. In animals, gluconeogenesis takes place mainly in the 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...

 and, to a lesser extent, in the cortex of kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

s. This process occurs during periods of fasting
Fasting
Fasting is primarily the act of willingly abstaining from some or all food, drink, or both, for a period of time. An absolute fast is normally defined as abstinence from all food and liquid for a defined period, usually a single day , or several days. Other fasts may be only partially restrictive,...

, starvation
Starvation
Starvation is a severe deficiency in caloric energy, nutrient and vitamin intake. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, death...

, low-carbohydrate diet
Low-carbohydrate diet
Low-carbohydrate diets or low-carb diets are dietary programs that restrict carbohydrate consumption usually for weight control or for the treatment of obesity. Foods high in digestible carbohydrates are limited or replaced with foods containing a higher percentage of proteins and fats...

s, or intense exercise and is highly endergonic
Endergonic
Endergonic means "absorbing energy in the form of work." Endergonic reactions are not spontaneous...

. For example, the pathway leading from pyruvate to glucose-6-phosphate requires 4 molecules of ATP and 2 molecules of GTP. Gluconeogenesis is often associated with ketosis
Ketosis
Ketosis is a state of elevated levels of ketone bodies in the body. It is almost always generalized throughout the body, with hyperketonemia, that is, an elevated level of ketone bodies in the blood. Ketone bodies are formed by ketogenesis when the liver glycogen stores are depleted...

. Gluconeogenesis is also a target of therapy for type II diabetes, such as metformin
Metformin
Metformin is an oral antidiabetic drug in the biguanide class. It is the first-line drug of choice for the treatment of type 2 diabetes, in particular, in overweight and obese people and those with normal kidney function. Its use in gestational diabetes has been limited by safety concerns...

, which inhibits glucose formation and stimulates glucose uptake by cells.

Entering the pathway


Lactate is transported back to the liver where it is converted into pyruvate by the Cori cycle
Cori cycle
The Cori cycle , named after its discoverers, Carl Cori and Gerty Cori, refers to the metabolic pathway in which lactate produced by anaerobic glycolysis in the muscles moves to the liver and is converted to glucose, which then returns to the muscles and is converted back to lactate.-Cycle:Muscular...

 using the enzyme lactate dehydrogenase
Lactate dehydrogenase
Lactate dehydrogenase is an enzyme present in a wide variety of organisms, including plants and animals.Lactate dehydrogenases exist in four distinct enzyme classes. Two of them are cytochrome c-dependent enzymes, each acting on either D-lactate or L-lactate...

. Pyruvate, the first designated substrate of the gluconeogenic pathway, can then be used to generate glucose.

All 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...

 intermediates, through conversion to oxaloacetate, amino acids other than lysine
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....

 or leucine
Leucine
Leucine is a branched-chain α-amino acid with the chemical formula HO2CCHCH2CH2. Leucine is classified as a hydrophobic amino acid due to its aliphatic isobutyl side chain. It is encoded by six codons and is a major component of the subunits in ferritin, astacin and other 'buffer' proteins...

, and glycerol can also function as substrates for gluconeogenesis. Transamination
Transamination
There are two chemical reactions known as transamination . The first is the reaction between an amino acid and an alpha-keto acid...

 or deamination
Deamination
Deamination is the removal of an amine group from a molecule. Enzymes which catalyse this reaction are called deaminases.In the human body, deamination takes place primarily in the liver, however glutamate is also deaminated in the kidneys. Deamination is the process by which amino acids are...

 of amino acids facilitates entering of their carbon skeleton into the cycle directly (as pyruvate or oxaloacetate), or indirectly via the citric acid cycle.

Whether fatty acid
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

s can be converted into glucose in animals has been a longstanding question in biochemistry. It is known that odd-chain fatty acids can be oxidized to yield propionyl CoA, a precursor for succinyl CoA, which can be converted to pyruvate and enter into gluconeogenesis. In plants, specifically seedlings, the glyoxylate cycle
Glyoxylate cycle
The glyoxylate cycle, a variation of the Tricarboxylic Acid Cycle, is an anabolic metabolic pathway occurring in plants, bacteria, protists, fungi and several microorganisms, such as E. coli and yeast. The glyoxylate cycle centers on the conversion of acetyl-CoA to succinate for the synthesis of...

 can be used to convert fatty acids (acetate
Acetate
An acetate is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. Most of the approximately 5 billion kilograms of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of polymers. In...

) into the primary carbon source of the organism. The glyoxylate cycle produces four-carbon dicarboxylic acids that can enter gluconeogenesis.

In 1995, researchers identified the glyoxylate cycle in nematodes. In addition, the glyoxylate enzymes malate synthase
Malate synthase
In enzymology, a malate synthase is an enzyme that catalyzes the chemical reactionThe 3 substrates of this enzyme are acetyl-CoA, H2O, and glyoxylate, whereas its two products are -malate and CoA....

 and isocitrate lyase
Isocitrate lyase
Isocitrate lyase , or ICL, is an enzyme in the glyoxylate cycle that catalyzes the cleavage of isocitrate to succinate and glyoxylate. Together with malate synthase, it bypasses the two decarboxylation steps of the tricarboxylic acid cycle and is used by bacteria, fungi, and plants.The systematic...

 have been found in animal tissues. Genes coding for malate synthase gene have been identified in other [metazoans] including arthropods, echinoderms, and even some vertebrates. Mammals found to possess these genes include monotremes (platypus) and marsupials (opossum) but not placental mammals. Genes for isocitrate lyase are found only in nematodes, in which, it is apparent, they originated in horizontal gene transfer from bacteria.

The existence of glyoxylate cycles in humans has not been established, and it is widely held that fatty acids cannot be converted to glucose in humans directly. However, carbon-14 has been shown to end up in glucose when it is supplied in fatty acids. Despite these findings, it is considered unlikely that the 2-carbon acetyl-CoA derived from the oxidation of fatty acids would produce a net yield of glucose via 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...

.

Glycerol
Glycerol
Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

, which is a part of the triacylglycerol molecule, can be used in gluconeogenesis.

Location


In humans, gluconeogenesis is restricted to the liver and to a lesser extent the kidney.

In all species, the formation of oxaloacetate from pyruvate and TCA cycle intermediates is restricted to the mitochondrion, and the enzymes that convert PEP to glucose are found in the cytosol. The location of the enzyme that links these two parts of gluconeogenesis by converting oxaloacetate to PEP, PEP carboxykinase, is variable by species: it can be found entirely within the mitochondria, entirely within the cytosol, or dispersed evenly between the two, as it is in humans. Transport of PEP across the mitochondrial membrane is accomplished by dedicated transport proteins; however no such proteins exist for oxaloacetate. Therefore species that lack intra-mitochondrial PEP, oxaloacetate must be converted into malate or asparate, exported from the mitochondrion, and converted back into oxaloacetate in order to allow gluconeogenesis to continue.

Pathway


Gluconeogenesis is a pathway consisting of eleven enzyme-catalyzed reactions. The pathway can begin in the mitochondria or cytoplasm, depending on the substrate being used. Many of the reactions are the reversible steps found in glycolysis
Glycolysis
Glycolysis is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+...

.
  • Gluconeogenesis begins in the mitochondria with the formation of oxaloacetate through carboxylation of pyruvate. This reaction also requires one molecule 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...

    , and is catalyzed by pyruvate carboxylase
    Pyruvate carboxylase
    Pyruvate carboxylase is an enzyme of the ligase class that catalyzes the irreversible carboxylation of pyruvate to form oxaloacetate .It is an important anaplerotic reaction that creates oxaloacetate from pyruvate...

    . This enzyme is stimulated by high levels of acetyl-CoA
    Acetyl-CoA
    Acetyl coenzyme A or acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. Its main function is to convey the carbon atoms within the acetyl group to the citric acid cycle to be oxidized for energy production. In chemical structure, acetyl-CoA is the thioester...

     (produced in β-oxidation in the liver) and inhibited by high levels of ADP.
  • Oxaloacetate is reduced
    Redox
    Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

     to malate
    Malate
    Malate is the ionized form of malic acid. It is an important chemical compound in biochemistry. In the C4 carbon fixation process, malate is a source of CO2 in the Calvin cycle....

     using NADH
    Nicotinamide adenine dinucleotide
    Nicotinamide adenine dinucleotide, abbreviated NAD, is a coenzyme found in all living cells. The compound is a dinucleotide, since it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine base and the other nicotinamide.In metabolism, NAD is involved...

    , a step required for transport out of the mitochondria.
  • Malate is oxidized
    Redox
    Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

     to oxaloacetate using NAD+ in the cytoplasm, where the remaining steps of gluconeogenesis occur.
  • Oxaloacetate is decarboxylated and phosphorylated to produce phosphoenolpyruvate
    Phosphoenolpyruvate
    Phosphoenolpyruvic acid , or phosphoenolpyruvate as the anion, is an important chemical compound in biochemistry. It has the high-energy phosphate bond found in living organisms, and is involved in glycolysis and gluconeogenesis...

     by phosphoenolpyruvate carboxykinase
    Phosphoenolpyruvate carboxykinase
    Phosphoenolpyruvate carboxykinase is an enzyme in the lyase family used in the metabolic pathway of gluconeogenesis. It converts oxaloacetate into phosphoenolpyruvate and carbon dioxide.It is found in two forms, cytosolic and mitochondrial....

    . One molecule of GTP
    Guanosine triphosphate
    Guanosine-5'-triphosphate is a purine nucleoside triphosphate. It can act as a substrate for the synthesis of RNA during the transcription process...

     is hydrolyzed to GDP
    Guanosine diphosphate
    Guanosine diphosphate, abbreviated GDP, is a nucleoside diphosphate. It is an ester of pyrophosphoric acid with the nucleoside guanosine. GDP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase guanine....

     during this reaction.
  • The next steps in the reaction are the same as reversed glycolysis. However, fructose-1,6-bisphosphatase converts fructose-1,6-bisphosphate to 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...

    , requiring one water molecule and releasing one phosphate. This is also the rate-limiting step of gluconeogenesis.
  • 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....

     is formed from 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...

     by phosphoglucoisomerase. Glucose-6-phosphate can be used in other metabolic pathways or dephosphorylated to free glucose. Whereas free glucose can easily diffuse in and out of the cell, the phosphorylated form (glucose-6-phosphate) is locked in the cell, a mechanism by which intracellular glucose levels are controlled by cells.
  • The final reaction of gluconeogenesis, the formation of glucose, occurs in the lumen
    Lumen (anatomy)
    A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...

     of the endoplasmic reticulum
    Endoplasmic reticulum
    The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...

    , where glucose-6-phosphate is hydrolyzed by glucose-6-phosphatase to produce glucose. Glucose is shuttled into the cytosol by glucose transporter
    Glucose transporter
    Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose over a plasma membrane. Because glucose is a vital source of energy for all life these transporters are present in all phyla...

    s located in the membrane of the endoplasmic reticulum.

Regulation


While most steps in gluconeogenesis are the reverse of those found in glycolysis
Glycolysis
Glycolysis is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+...

, three regulated and strongly exergonic reactions are replaced with more kinetically favorable reactions. Hexokinase
Hexokinase
A hexokinase is an enzyme that phosphorylates a six-carbon sugar, a hexose, to a hexose phosphate. In most tissues and organisms, glucose is the most important substrate of hexokinases, and glucose-6-phosphate the most important product....

/glucokinase
Glucokinase
Glucokinase is an enzyme that facilitates phosphorylation of glucose to glucose-6-phosphate. Glucokinase occurs in cells in the liver, pancreas, gut, and brain of humans and most other vertebrates...

, phosphofructokinase
Phosphofructokinase
Phosphofructokinase-1 is the most important regulatory enzyme of glycolysis. It is an allosteric enzyme made of 4 subunits and controlled by many activators and inhibitors...

, and pyruvate kinase
Pyruvate kinase
Pyruvate kinase is an enzyme involved in glycolysis. It catalyzes the transfer of a phosphate group from phosphoenolpyruvate to ADP, yielding one molecule of pyruvate and one molecule of ATP.-Reaction:The reaction with pyruvate kinase:...

 enzymes of glycolysis are replaced with glucose-6-phosphatase, fructose-1,6-bisphosphatase, and PEP carboxykinase. This system of reciprocal control allow glycolysis and gluconeogenesis to inhibit each other and prevent the formation of a futile cycle
Futile cycle
A futile cycle, also known as a substrate cycle, occurs when two metabolic pathways run simultaneously in opposite directions and have no overall effect other than to dissipate energy in the form of heat...

.

The majority of the enzymes responsible for gluconeogenesis are found in the cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...

; the exceptions are mitochondrial pyruvate carboxylase
Pyruvate carboxylase
Pyruvate carboxylase is an enzyme of the ligase class that catalyzes the irreversible carboxylation of pyruvate to form oxaloacetate .It is an important anaplerotic reaction that creates oxaloacetate from pyruvate...

 and, in animals, phosphoenolpyruvate carboxykinase
Phosphoenolpyruvate carboxykinase
Phosphoenolpyruvate carboxykinase is an enzyme in the lyase family used in the metabolic pathway of gluconeogenesis. It converts oxaloacetate into phosphoenolpyruvate and carbon dioxide.It is found in two forms, cytosolic and mitochondrial....

. The latter exists as an isozyme located in both the mitochondrion
Mitochondrion
In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometers in diameter...

 and the cytosol
Cytosol
The cytosol or intracellular fluid is the liquid found inside cells, that is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondrion into compartments....

. The rate of gluconeogenesis is ultimately controlled by the action of a key enzyme, fructose-1,6-bisphosphatase, which is also regulated through signal transduction by cAMP
Cyclic adenosine monophosphate
Cyclic adenosine monophosphate is a second messenger important in many biological processes...

 and its phosphorylation.

Most factors that regulate the activity of the gluconeogenesis pathway do so by inhibiting the activity or expression of key enzymes. However, both acetyl CoA and citrate
Citrate
A citrate can refer either to the conjugate base of citric acid, , or to the esters of citric acid. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate.-Other citric acid ions:...

 activate gluconeogenesis enzymes (pyruvate carboxylase and fructose-1,6-bisphosphatase, respectively). Due to the reciprocal control of the cycle, acetyl-CoA and citrate also have inhibitory roles in the activity of pyruvate kinase
Pyruvate kinase
Pyruvate kinase is an enzyme involved in glycolysis. It catalyzes the transfer of a phosphate group from phosphoenolpyruvate to ADP, yielding one molecule of pyruvate and one molecule of ATP.-Reaction:The reaction with pyruvate kinase:...

.

Global control of gluconeogenesis is mediated 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...

 (released when blood glucose is low); it triggers phosphorylation of enzymes and regulatory proteins by Protein Kinase A (a cyclic AMP regulated kinase) resulting in inhibition of glycolysis and stimulation of gluconeogenesis, thus bringing blood glucose levels up.

External links