glycogenesis

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WordNet

1. the formation in animals of glycogen from glucose
2. the conversion of glucose to glycogen when the glucose in the blood exceeds the demand

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/12/21 14:12:50」(JST)

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Not to be confused with Gluconeogenesis.

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 carbohydrate-containing meal.

Steps

• Glucose is converted into glucose-6-phosphate by the action of glucokinase or hexokinase.
• Glucose-6-phosphate is converted into glucose-1-phosphate by the action of Phosphoglucomutase, passing through an obligatory intermediate step of glucose-1,6-bisphosphate.
• Glucose-1-phosphate is converted into UDP-glucose by the action of Uridyl Transferase (also called UDP-glucose pyrophosphorylase) and pyrophosphate is formed, which is hydrolysed by pyrophosphatase into 2 molecules of Pi.
• Glucose molecules are assembled in a chain by glycogen synthase, which must act on a pre-existing glycogen primer or glycogenin (small protein that forms the primer). The mechanism for joining glucose units is that glycogen synthase binds to UDPG, causing it to break down into an oxonium ion, also formed in glycogenolysis. This oxonium ion can readily add to the 4-hydroxyl group of a glucosyl residue on the 4 end of the glycogen chain.
• Branches are made by branching enzyme (also known as amylo-α(1:4)→α(1:6)transglycosylase), which transfers the end of the chain onto an earlier part via α-1:6 glycosidic bond, forming branches, which further grow by addition of more α-1:4 glycosidic units.

Metabolism of common monosaccharides, including glycolysis, gluconeogenesis, glycogenesis and glycogenolysis

Control and regulations

Glycogenesis responds to hormonal control.

One of the main forms of control is the varied phosphorylation of glycogen synthase and glycogen phosphorylase. This is regulated by enzymes under the control of hormonal activity, which is in turn regulated by many factors. As such, there are many different possible effectors when compared to allosteric systems of regulation.

Epinephrine (Adrenaline)

See also: Epinephrine

Glycogen phosphorylase is activated by phosphorylation, whereas glycogen synthase is inhibited.

Glycogen phosphorylase is converted from its less active "b" form to an active "a" form by the enzyme phosphorylase kinase. This latter enzyme is itself activated by protein kinase A and deactivated by phosphoprotein phosphatase-1.

Protein kinase A itself is activated by the hormone adrenaline. Epinephrine binds to a receptor protein that activates adenylate cyclase. The latter enzyme causes the formation of cyclic AMP from ATP; two molecules of cyclic AMP bind to the regulatory subunit of protein kinase A, which activates it allowing the catalytic subunit of protein kinase A to dissociate from the assembly and to phosphorylate other proteins.

Returning to glycogen phosphorylase, the less active "b" form can itself be activated without the conformational change. 5'AMP acts as an allosteric activator, whereas ATP is an inhibitor, as already seen with phosphofructokinase control, helping to change the rate of flux in response to energy demand.

Epinephrine not only activates glycogen phosphorylase but also inhibits glycogen synthase. This amplifies the effect of activating glycogen phosphorylase. This inhibition is achieved by a similar mechanism, as protein kinase A acts to phosphorylate the enzyme, which lowers activity. This is known as co-ordinate reciprocal control. Refer to glycolysis for further information of the regulation of glycogenesis.

Insulin

See also: Insulin

Insulin has an antagonistic effect to adrenaline. When insulin binds on the G protein-coupled receptor, the alpha subunit of GDP in the G protein changes to GTP and dissociates from the inhibitory beta and gamma subunits. The alpha subunit binds on adenylyl cyclase to inhibit its activity. As a result, less cAMP then less protein kinase A will be produced. Thus, glycogen synthase, one of the targets of protein kinase A, will be in non-phosphorylated form, which is the active form of glycogen synthase. Active glycogen synthase can decrease the blood glucose level after a full meal

Calcium ions

Calcium ions or cyclic AMP (cAMP) act as secondary messengers. This is an example of negative control. The calcium ions activate phosphorylase kinase. This activates glycogen phosphorylase and inhibits glycogen synthase.

See also

• Glycogenolysis
• Glycogen synthase
• Glycogen storage disease

External links

• The chemical logic of glycogen synthesis

UpToDate Contents

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• 1. リソソーム酸α-グルコシダーゼ欠損症（ポンペ病、糖原病II型、酸マルターゼ欠損症） lysosomal acid alpha glucosidase deficiency pompe disease glycogen storage disease ii acid maltase deficiency

English Journal

• Glycogen Synthase in Sertoli Cells: More Than Glycogenesis?

• Maldonado R1, Mancilla H1, Villarroel-Espíndola F1, Slebe F2, Slebe JC1, Méndez R2,3, Guinovart JJ2,4,5, Concha II6.
• Journal of cellular biochemistry.J Cell Biochem.2016 Nov;117(11):2597-607. doi: 10.1002/jcb.25554. Epub 2016 Apr 7.
• Sertoli cell metabolism actively maintains the nutritional needs of germ cells. It has been described that after glucose incorporation in Sertoli cells, less than 1% is converted to glycogen suggesting low levels of glycogen synthase activity. Phosphorylation of muscle glycogen synthase (MGS) at ser
• PMID 27017955

• Black ginseng extract exerts anti-hyperglycemic effect via modulation of glucose metabolism in liver and muscle.

• Seo YS1, Shon MY2, Kong R1, Kang OH1, Zhou T1, Kim DY2, Kwon DY3.
• Journal of ethnopharmacology.J Ethnopharmacol.2016 Aug 22;190:231-40. doi: 10.1016/j.jep.2016.05.060. Epub 2016 May 31.
• ETHNOPHARMACOLOGICAL RELEVANCE: Ginseng (Panax ginseng C. A. Meyer, Araliaceae) has been used as a traditional medicine for thousands of years for the treatment of a wide variety of diseases, including diabetes. Processed ginseng named Black ginseng exhibits more potent biological activities than wh
• PMID 27260409

• MicroRNA-20a-5p contributes to hepatic glycogen synthesis through targeting p63 to regulate p53 and PTEN expression.

• Fang W1,2, Guo J2, Cao Y2, Wang S2, Pang C2, Li M2, Dou L2, Man Y2, Huang X2, Shen T2, Li J1,2.
• Journal of cellular and molecular medicine.J Cell Mol Med.2016 Aug;20(8):1467-80. doi: 10.1111/jcmm.12835. Epub 2016 Mar 28.
• Recently, it is implicated that aberrant expression of microRNAs (miRs) is associated with insulin resistance. However, the role of miR-17 family in hepatic insulin resistance and its underlying mechanisms remain unknown. In this study, we provided mechanistic insight into the effects of miR-20a-5p,
• PMID 27019188

Japanese Journal

• Uterine Glycogen Metabolism in Mink during Estrus, Embryonic Diapause and Pregnancy

• DEAN Matthew,HUNT Jason,MCDOUGALL Lisa,ROSE Jack
• Journal of Reproduction and Development, 2014
• … While glycogen phosphorylase protein was detected during estrus and diapause, glycogen synthase was almost undetectable after estrus, which probably contributed to a higher glycogenolysis/glycogenesis ratio during diapause. …
• NAID 130004687240

• Effects of celiac superior mesenteric ganglionectomy on glucose homeostasis and hormonal changes during oral glucose tolerance testing in rats

• Kumakura Atsushi,Shikuma Junpei,Ogihara Norikazu,Eiki Jun-ichi,Kanazawa Masao,Notoya Yoko,Kikuchi Masatoshi,Odawara Masato
• Endocrine Journal 60(4), 525-531, 2013
• … Glycogenesis and glycogenolysis are regulated by various mechanisms including hormones, the sympathetic and parasympathetic nervous systems and the hepatic glucose content. …
• NAID 130004443868

• タンナーゼ活性を有する乳酸菌を利用した新規プロバイオティクスの開発

• 大澤 朗
• 腸内細菌学雑誌 = Journal of intestinal microbiology 25(1), 1-5, 2011-01-01
• 緑茶やワインに含まれるカテキン類は強い抗酸化力を持ち，体内で発生する活性酸素を「無害化」して発ガンを抑制したり，コレステロールの酸化を防いで動脈硬化を予防したり，また糖質分解酵素の働きを阻害して過剰な血糖値の上昇を抑える等，ヒトの健康維持・増進・疾病予防に非常に有用な効果をもたらすことが知られている．緑茶に含まれる主なカテキン類は，没食子酸エステル構造をもつ加水分解型タンニン様のエピガロカテキンガ …
• NAID 10027792953

Related Links

• Glycogenesis | definition of glycogenesis by Medical dictionary

glycogenesis [gli″ko-jen´ĕ-sis] the conversion of glucose to glycogen for storage in the liver. adj., adj glycogenet´ic. gly·co·gen·e·sis (glī'kō-jen'ĕ-sis), Formation of glycogen from d-glucose by means of glycogen synthase and dextrin ...

• glycogenesis | biochemistry | Britannica.com

The formation of glycogen, the primary carbohydrate stored in the liver and muscle cells of animals, from glucose. Glycogenesis takes place when blood glucose levels are sufficiently... ... We welcome suggested improvements to ...

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