Glucagon

serum glucagon
Glucagon is a peptide hormone, produced by alpha cells of the pancreas.wikipedia
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Pancreas

pancreaticexocrine pancreaspancreatic development
Glucagon is a peptide hormone, produced by alpha cells of the pancreas.
As an endocrine gland, it functions mostly to regulate blood sugar levels, secreting the hormones insulin, glucagon, somatostatin, and pancreatic polypeptide.

Insulin

insulin geneINShuman insulin
Its effect is opposite to that of insulin, which lowers extracellular glucose.
Their neighboring alpha cells, by taking their cues from the beta cells, secrete glucagon into the blood in the opposite manner: increased secretion when blood glucose is low, and decreased secretion when glucose concentrations are high.

Secretin family

glucagon hormone familySecretin-glucagon familySecretins
Glucagon belongs to the secretin family of hormones.
Glucagon/GIP/secretin/VIP hormones are a family of evolutionarily related peptide hormones that regulate activity of G-protein coupled receptors from secretin receptor family.

Proglucagon

glucagon precursorspreproglucagonGCG
It is produced from proglucagon, encoded by the GCG gene.
Proglucagon is a precursor of glucagon, and several other components.

Glucagon receptor

GCGRglucagonreceptors, glucagon
Liver cells (hepatocytes) have glucagon receptors. Glucagon binds to the glucagon receptor, a G protein-coupled receptor, located in the plasma membrane.
The glucagon receptor is a 62 kDa protein that is activated by glucagon and is a member of the class B G-protein coupled family of receptors, coupled to G alpha i, G s and to a lesser extent G alpha q. Stimulation of the receptor results in activation of adenylate cyclase and increased levels of intracellular cAMP.

Lipolysis

lipolyticfat metabolizationlipolyzed
Glucagon also regulates the rate of glucose production through lipolysis.
Lipolysis is induced by several hormones, including glucagon, epinephrine, norepinephrine, growth hormone, atrial natriuretic peptide, brain natriuretic peptide, and cortisol.

Glucagon (medication)

glucagonmedication
It is also used as a medication to treat a number of health conditions.
It is a manufactured form of the glucagon hormone.

Protein kinase A

PKAcAMP-dependent protein kinasecyclic AMP-dependent protein kinase
Adenylate cyclase manufactures cyclic adenosine monophosphate (cyclic AMP or cAMP), which activates protein kinase A (cAMP-dependent protein kinase).
Extracellular hormones such as glucagon and epinephrine begin an intracellular signalling cascade that triggers protein kinase A activation by first binding to a G protein–coupled receptor (GPCR) on the target cell.

Glucose

dextroseD-glucose D -glucose
It works to raise the concentration of glucose and fatty acids in the bloodstream, and is considered to be the main catabolic hormone of the body. Glucagon causes the liver to convert stored glycogen into glucose, which is released into the bloodstream. Glucagon generally elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis.
The glucose content of the blood is regulated by the hormones insulin, incretin and glucagon.

Glycogen

glycogen depositsglycogen (n)glycogen deposits
Glucagon causes the liver to convert stored glycogen into glucose, which is released into the bloodstream.
Glucagon, another hormone produced by the pancreas, in many respects serves as a countersignal to insulin.

Cyclic adenosine monophosphate

cAMPcyclic AMP3',5'-cyclic AMP
Adenylate cyclase manufactures cyclic adenosine monophosphate (cyclic AMP or cAMP), which activates protein kinase A (cAMP-dependent protein kinase).
cAMP is a second messenger, used for intracellular signal transduction, such as transferring into cells the effects of hormones like glucagon and adrenaline, which cannot pass through the plasma membrane.

Peptide hormone

peptide hormonesprotein hormonepolypeptide hormone
Glucagon is a peptide hormone, produced by alpha cells of the pancreas.

Glycolysis

glycolyticglycolytic pathwayEmbden–Meyerhof pathway
Glucagon turns off glycolysis in the liver, causing glycolytic intermediates to be shuttled to gluconeogenesis.
When the blood sugar falls the pancreatic beta cells cease insulin production, but, instead, stimulate the neighboring pancreatic alpha cells to release glucagon into the blood.

Catabolism

cataboliccatabolizedcatabolize
It works to raise the concentration of glucose and fatty acids in the bloodstream, and is considered to be the main catabolic hormone of the body.
The so-called classic catabolic hormones known since the early 20th century are cortisol, glucagon, and adrenaline (and other catecholamines).

G protein-coupled receptor

G-protein coupled receptorG protein-coupled receptorsGPCR
Glucagon binds to the glucagon receptor, a G protein-coupled receptor, located in the plasma membrane.
glucagon;

Pancreatic islets

islets of Langerhanspancreatic isletislet cell
The hormone is synthesized and secreted from alpha cells (α-cells) of the islets of Langerhans, which are located in the endocrine portion of the pancreas.

Alpha cell

alpha cellsalphaglucagon-secreting cells
Glucagon is a peptide hormone, produced by alpha cells of the pancreas. The hormone is synthesized and secreted from alpha cells (α-cells) of the islets of Langerhans, which are located in the endocrine portion of the pancreas.
They make up to 20% of the human islet cells synthesizing and secreting the peptide hormone glucagon, which elevates the glucose levels in the blood.

Glycogenolysis

breakdown of glycogenbreakdownglycogen degradation
Glucagon generally elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis.
Glycogenolysis is regulated hormonally in response to blood sugar levels by glucagon and insulin, and stimulated by epinephrine during the fight-or-flight response.

Hypoglycemia

low blood sugarhypoglycaemiahypoglycemic
Hormonal defense mechanisms (adrenaline and glucagon) are normally activated as it drops below a threshold level (about 55 mg/dL (3.0 mM) for most people), producing the typical hypoglycemic symptoms of shakiness and dysphoria.

Gamma-Aminobutyric acid

GABAγ-aminobutyric acidGABAergic
The β-cells secrete GABA along with insulin and the GABA binds to GABA receptors on the neighboring islet α-cells and inhibits them from secreting glucagon (which would counteract insulin's effects).

Pyruvate kinase

Glucagon stimulation of PKA also inactivates the glycolytic enzyme pyruvate kinase in hepatocytes.
In the liver, glucagon and epinephrine activate protein kinase A, which serves as a covalent modifier by phosphorylating and deactivating pyruvate kinase.

Gluconeogenesis

gluconeogenicgluconeogenic pathwayglucogenic
Glucagon generally elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis.
Global control of gluconeogenesis is mediated by glucagon (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.

Adrenaline

epinephrineadrenaline junkieadrenalin
β adrenergic receptor binding triggers glucagon secretion in the pancreas, increased adrenocorticotropic hormone (ACTH) secretion by the pituitary gland, and increased lipolysis by adipose tissue.

G protein

G-proteinG proteinsG-proteins
The conformation change in the receptor activates G proteins, a heterotrimeric protein with α, β, and γ subunits.

Glycogen phosphorylase

Liver glycogen phosphorylaseliver glycogenliver phosphorylase
This enzyme, in turn, activates phosphorylase kinase, which then phosphorylates glycogen phosphorylase b (PYG b), converting it into the active form called phosphorylase a (PYG a).
Hormones such as epinephrine, insulin and glucagon regulate glycogen phosphorylase using second messenger amplification systems linked to G proteins.