Gluconeogenesis pathway with key molecules and enzymes. Many steps are the opposite of those found in the glycolysis.

Gluconeogenesis is a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as pyruvate, lactate, glycerol, and glucogenic amino acids. Glycolysis is the sequence of reactions that converts glucose into pyruvate with the concomitant production of a relatively small amount of ATP. The word is derived from Greek γλυκύς (sweet) and λύσις (letting loose). ... In biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. ... Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. ... Pyruvate (CH3COCOO−) is the ionized form of pyruvic acid. ... For the production of milk by mammals, see Lactation. ... Glycerine, Glycerin redirects here. ... A glucogenic amino acid is an amino acid that can be converted into glucose through gluconeogenesis. ...

The vast majority of gluconeogenesis takes place in the liver and, to a smaller extent, in the cortex of kidneys. This process occurs during periods of fasting, starvation, or intense exercise and is highly endergonic. Gluconeogenesis is often associated with ketosis. Gluconeogenesis is also a target of therapy for type II diabetes, such as metformin, which inhibit glucose formation and stimulate glucose uptake by cells.^[1] The liver is the largest internal organ in the human body, and is an organ present in vertebrates and some other animals. ... The kidneys are the organs that filter wastes (such as urea) from the blood and excrete them, along with water, as urine. ... Fasting is primarily the act of willingly abstaining from some or all food, drink, or both, for a period of time. ... This article is about extreme malnutrition. ... The term Exercise can refer to: Physical exercise such as running or strength training Exercise (options), the financial term for enacting and terminating a contract Category: ... Endergonic means absorbing energy in the form of work. ... Ketosis (IPA pronunciation: ) is a stage in metabolism occurring when the liver converts fat into fatty acids and ketone bodies which can be used by the body for energy. ... Metformin (INN; trade names Glucophage, Diabex, Diaformin, Fortamet, Riomet, Glumetza and others) is an anti-diabetic drug from the biguanide class of oral hypoglycemic agents. ...

Entering the pathway

Several non-carbohydrate carbon substrates can enter the gluconeogenesis pathway. One common substrate is lactic acid, formed during anaerobic respiration in skeletal muscle. Lactate is transported back to the liver where it is converted into pyruvate by the Cori cycle using the enzyme lactate dehydrogenase. Pyruvate, the first designated substrate of the gluconeogenic pathway, can then be used to generate glucose.^[2] For other uses, see Carbon (disambiguation). ... For other uses, see Substrate. ... In biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. ... For the production of milk by mammals, see Lactation. ... Anaerobic respiration refers to the oxidation of molecules in the absence of oxygen to produce energy, in opposition to Aerobic respiration which does use oxygen. ... Pyruvate (CH3COCOO−) is the ionized form of pyruvic acid. ... The Cori cycle, named after its discoverers, Carl Cori and Gerty Cori, refers to the cycling of lactate produced by red blood cells and muscle (during anaerobic respiration) back into glucose. ... Lactate dehydrogenase (LDH) is an enzyme (EC 1. ...

All citric acid cycle intermediates, through conversion to oxaloacetate, amino acids other than lysine or leucine, and glycerol can also function as substrates for gluconeogenesis.^[3] Amino acids must have their amino group removed by transamination or deamination before entering the cycle directly (as pyruvate or oxaloacetate), or indirectly via the citric acid cycle. Overview of the citric acid cycle The citric acid cycle (also known as the tricarboxylic acid cycle, the TCA cycle, or the Krebs cycle, after Hans Adolf Krebs who identified the cycle) is a series of chemical reactions of central importance in all living cells that use oxygen as part... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... Lysine is one of the 20 amino acids normally found in proteins. ... Leucine is one of the 20 most common amino acids and coded for by DNA. It is isomeric with isoleucine. ... Transamination is the reaction between an amino acid and an alpha-keto acid. ... Deamination is the removal of an amine group from a molecule. ...

Fatty acids cannot be converted into glucose in animals, the exception being odd-chain fatty acids which yield propionyl CoA, a precursor for succinyl CoA. In plants, specifically in seedlings, the glyoxylate cycle can be used to convert fatty acids (acetate) into the primary carbon source of the organism. The glyoxylate cycle produces four-carbon dicarboxylic acids that can enter gluconeogenesis.^[4] Glycerol, which is a part of all triacylglycerols, can also be used in gluconeogenesis. In organisms in which glycerol is derived from glucose (e.g., humans and other mammals), glycerol is sometimes not considered a true gluconeogenic substrate, as it cannot be used to generate new glucose. Not to be confused with fats. ... Not to be confused with fats. ... Propionyl-CoA is a coenzyme A derivative of propionic acid. ... Succinyl-CoA (coenzyme A is grey) Succinyl-Coenzyme A, generally abbreviated as Succinyl-CoA is a combination of succinic acid and coenzyme A. Source It is an important intermediate in the citric acid cycle, where is it synthetised from α-Ketoglutarate by α-ketoglutarate dehydrogenase through decarboxylation. ... Overview of the Glyoxylate Cycle The glyoxylate cycle is a metabolic pathway occurring in plants, certain vertebrates, and several microorganisms, such as E. coli and yeast. ... For other uses, see Acetate (disambiguation). ... Glycerine, Glycerin redirects here. ... This article is about lipid molecules, for FAT see File Allocation Table. ...

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 reversible steps found in glycolysis.

• Gluconeogenesis begins in the mitochondria with the formation of oxaloacetate through carboxylation of pyruvate at the expense of one molecule of ATP. This reaction is catalyzed by pyruvate carboxylase, which is stimulated by high levels of acetyl-CoA (when fatty acid oxidation is high in the liver) and inhibited by high levels of ADP.
• Oxaloacetate must then be reduced into malate using NADH in order to be transported out of the mitochondria.
• In the cytoplasm, malate is oxidized to oxaloacetate using NAD⁺, where the remaining steps of gluconeogenesis occur.
• Oxaloacetate is then decarboxylated and phosphorylated to produce phosphoenolpyruvate by phosphoenolpyruvate carboxykinase. One molecule of GTP is hydrolyzed to GDP in the course of 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. The purpose of this reaction is to overcome the large negative ΔG.
• Glucose-6-phosphate is formed from fructose-6-phosphate by phosphoglucoisomerase. Glucose-6-phosphate can then be used for glucose generation or in other metabolic pathways. Free glucose is not generated automatically because glucose, unlike glucose-6-phosphate, tends to freely diffuse out of the cell.
• The final reaction of gluconeogenesis, the formation of glucose, is carried out in the lumen of the endoplasmic reticulum. Glucose-6-phosphate is hydrolyzed by glucose-6-phosphatase to produce glucose. Glucose is then shuttled into the cytosol by glucose transporters located in the membrane of the endoplasmic reticulum.

Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... Pyruvate carboxylase is an enzyme of the ligase class that catalyzes the reversible carboxylation of pyruvate to form oxaloacetate. ... Categories: Biochemistry stubs | Thiols ... ed|other uses|reduction}} Illustration of a redox reaction Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... Malate (O−OC-CH2-CH(OH)-COO−) is the ionized form of malic acid. ... Nicotinamide adenine dinucleotide (NAD+ or in older notation DPN+) is an important coenzyme found in cells. ... ed|other uses|reduction}} Illustration of a redox reaction Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... Nicotinamide adenine dinucleotide (NAD+ or in older notation DPN+) is an important coenzyme found in cells. ... Name Phosphoenolpyruvate; Phosphoenolpyruvic acid; PEP Formula C3H5O6P Mass 167. ... Phosphoenolpyruvate carboxylase (or PEPCase) is an enzyme in the family of carboxy-lyases. ... Guanosine triphosphate (GTP) is also known as guanosine-5-triphosphate. ... Glycolysis is the sequence of reactions that converts glucose into pyruvate with the concomitant production of a relatively small amount of ATP. The word is derived from Greek γλυκύς (sweet) and λύσις (letting loose). ... Fructose bisphosphatase (EC 3. ... Fructosephosphates are sugar phosphates based upon fructose. ... Fructosephosphates are sugar phosphates based upon fructose. ... Glucose 6-phosphate is glucose sugar phosphorylated on carbon 6. ... Fructosephosphates are sugar phosphates based upon fructose. ... Symbol(s): GPI Genetic data Locus: Chr. ... Lumen can mean: Lumen (unit), the SI unit of luminous flux Lumen (anatomy), the cavity or channel within a tubular structure Thylakoid lumen, the inner membrane space of the chloroplast 141 Lumen, an asteroid discovered by the French astronomer Paul Henry in 1875 Lumen (band), an American post-rock band... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ... Glucose 6-phosphatase is an enzyme in the glycogenolysis pathway that removes the phosphate from glucose 6-phosphate. ...

Regulation

While most steps in gluconeogenesis are the reverse of those found in glycolysis, three regulated and strongly exergonic reactions are replaced with more kinetically favorable reactions. Hexokinase/glucokianse, phosphofructokinase, and 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. Glycolysis is the sequence of reactions that converts glucose into pyruvate with the concomitant production of a relatively small amount of ATP. The word is derived from Greek γλυκύς (sweet) and λύσις (letting loose). ... A Futile cycle is when two metabolic pathways run simultaneously in opposite directions and have no overall effect other than wasting energy. ...

The majority of the enzymes responsible for gluconeogenesis are found in the cytoplasm; the exceptions are mitochondrial pyruvate carboxylase, and, in animals, phosphoenolpyruvate carboxykinase. The latter exists as an isozyme located in both the mitochondrion and the cytosol.^[5] As there is no known mechanism to transport phosphoenolpyruvate from the mitochondrion into the cytosol, the cytosolic enzyme is believed to be the isozyme important for gluconeogenesis. The rate of gluconeogenesis is ultimately controlled by the action of a key enzyme, fructose-1,6-bisphosphatase, which is also regulated through signal tranduction by cAMP and its phosphorylation. Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = blend) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... Schematic showing the cytoplasm, with major components of a typical animal cell. ... Pyruvate carboxylase is an enzyme of the ligase class that catalyzes the reversible carboxylation of pyruvate to form oxaloacetate. ... Phosphoenolpyruvate carboxylase (or PEPCase) is an enzyme in the family of carboxy-lyases. ... Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organelle that is found in most eukaryotic cells. ... The cytosol (cf. ... Name Phosphoenolpyruvate; Phosphoenolpyruvic acid; PEP Formula C3H5O6P Mass 167. ... Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organelle that is found in most eukaryotic cells. ... Fructose bisphosphatase (EC 3. ... Camp may mean: Gatherings of people: Campsite Temporary settlement of a band of foragers. ...

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 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. Acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. ... Chemical strucutre of citric acid. ... Pyruvate kinase is an enzyme involved in glycolysis. ...

References

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... “PDF” redirects here. ... A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to...

External links

• Overview at indstate.edu
• Interactive diagram at uakron.edu

v • d • e Metabolism map Glycerine, Glycerin redirects here. ... Glycerol kinase is a phosphotransferase enzyme involved in lipolysis. ... Phosphofructokinase-2 (PFK2) is one activity of a bifunctional enzyme (EC 2. ... Fructose-2,6-bisphosphatase is an enzyme that catalyzes the following reaction: fructose-2,6-bisphosphate + H2O ---> fructose-6-phosphate + phosphate ion Fructose-2,6-bisphosphatase is important in regulation of gluconeogenesis & glycolysis as it catalyzes the dephosphorylation of fructose-2,6-bisphosphate, which activates phosphofructokinase-1 (a critical enzyme... Symbol(s): BPGM Genetic data Locus: Chr. ... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ... Image File history File links Metabolism_790px_partly_labeled. ... Glucuronate metabolism Pentose interconversion Inositol metabolism Cellulose and sucrose metabolism Starch and glycogen metabolism Other sugar metabolism Pentose phosphate pathway Glycolysis and Gluconeogenesis Amino sugars metabolism Small amino acid synthesis Branched amino acid synthesis Purine biosynthesis Histidine metabolism Aromatic amino acid synthesis Pyruvate decarboxylation Anaerobic respiration Fatty acid metabolism Urea cycle Aspartate amino acid group synthesis Porphyrins and corrinoids metabolism Citric acid cycle Glutamate amino acid group synthesis Pyrimidine biosynthesis  v • d • e  All pathway labels on this image are links, simply click to access the article. A high resolution labeled version of this image is available here.