View source for Chemistry:Glucose-6-phosphate

{| align="right" width="300" border="1" cellspacing="0" cellpadding="3" style="margin: 0 0 0 0.5em; background: #FFFFFF; border-collapse: collapse"
|-
| align="center" colspan="2" | [[Image:Glucose-6-phosphate-skeletal.png|120px|Glucose-6-phosphate]][[Image:Glucose-6-phosphate-3D-vdW.png|120px|Glucose-6-phosphate]] <br/> ''Glucose-6-phosphate''
|-
| align="center" colspan="2" | '''Chemical name''' <br/>D-glucose-6-phosphate
|- style="border-top: 3px solid gray"
! bgcolor="#ffddaa" colspan="2" | General
|-
| bgcolor="#ffeedd" | [[Chemical formula]]
| C<sub>6</sub>H<sub>13</sub>O<sub>9</sub>P
|-
| bgcolor="#ffeedd" | [[Molecular weight]]
| 260.14 g/mol
|-
| bgcolor="#ffeedd" | Appearance
| ?
|-
| bgcolor="#ffeedd" | CAS number
| 56-73-5
|-
| bgcolor="#ffeedd" | MSDS
| Glucose-6-phosphate MSDS
|-
! bgcolor="#ffeedd" colspan="2" | Other names
|-
| colspan="2" |
* '''D-glucose-6-P'''
* '''glucose-6-P'''
* '''D-glucose-6-phosphate'''
|-
! bgcolor="#ffddaa" colspan="2" | Physical properties
|-
| bgcolor="#ffeedd" | [[Physics:Density|Density]] and [[Physics:Phase (matter)|phase]] at STP
| ?
|-
| bgcolor="#ffeedd" | [[Physics:Solubility|Solubility]]
| ?
|-
| bgcolor="#ffeedd" | [[Physics:Specific gravity|Specific gravity]]
| ?
|-
| bgcolor="#ffeedd" | [[Physics:Crystal structure|Crystal structure]]
| ?
|-
| bgcolor="#ffeedd" | pH (10% [[Physics:Solution|solution]] with [[Chemistry:Water|water]])<br/>(pKa)
| ?
|-
| bgcolor="#ffeedd" | Acidity constant<br/>(pKa)
| ?
|-
| bgcolor="#ffeedd" | Thermal decomposition
| ? K (? °C)
|-
! bgcolor="#ffddaa" colspan="2" | Phase behavior
|-
| bgcolor="#ffeedd" | [[Physics:Melting point|Melting point]]
| ?
|-
| bgcolor="#ffeedd" | [[Physics:Boiling point|Boiling point]]
| ?
|-
| bgcolor="#ffeedd" | [[Physics:Triple point|Triple point]]
| ?
|-
| bgcolor="#ffeedd" | Critical point
| ?
|-
| bgcolor="#ffeedd" | Heat of fusion<br/>(Δ<sub>fus</sub>H)
| ?
|-
| bgcolor="#ffeedd" | [[Physics:Entropy of fusion|Entropy of fusion]]<br/>(Δ<sub>fus</sub>S)
| ?
|-
| bgcolor="#ffeedd" | Heat of vaporization<br/>(Δ<sub>vap</sub>H)
| ?
|-
! bgcolor="#ffddaa" colspan="2" | Safety
|-
| bgcolor="#ffeedd" | Ingestion
| ?
|-
| bgcolor="#ffeedd" | Inhalation
| ?
|-
| bgcolor="#ffeedd" | Skin
| ?
|-
| bgcolor="#ffeedd" | Eyes
| ?
|-
| bgcolor="#ffeedd" | [[Physics:Flash point|Flash point]]
| ?
|-
| bgcolor="#ffeedd" | [[Physics:Autoignition temperature|Autoignition temperature]]
| ?
|-
| bgcolor="#ffeedd" | Explosive limits
| ?
|-
| bgcolor="#ffeedd" | OSHA Permissible Exposure Limit<br/>(PEL)
| ?
|-
| bgcolor="#ffeedd" | NIOSH Immediate Danger to Life and Health<br/>(IDLH)
| ?
|-
! bgcolor="#ffeedd" colspan="2" | Precautions
|-
| colspan="2" |
* '''Hazards''':
** N/A
* '''Personal protection''':
** N/A
* '''Reacts with''':
** N/A
* '''Storage''':
** N/A
|- style="border-top: 3px solid gray"
! bgcolor="#ffddaa" colspan="2" | [[Solid]] properties
|-
| bgcolor="#ffeedd" | Standard enthalpy change of formation<br/>(Δ<sub>f</sub>H<sup>0</sup><sub>solid</sub>)
| ?
|-
| bgcolor="#ffeedd" | [[Physics:Standard molar entropy|Standard molar entropy]]<br/>(S<sup>0</sup><sub>solid</sub>)
| ?
|-
| bgcolor="#ffeedd" | Heat capacity<br/>(C<sub>p</sub>)
| ?
|-
! bgcolor="#ffddaa" colspan="2" | [[Liquid]] properties
|-
| bgcolor="#ffeedd" | Δ<sub>f</sub>H<sup>0</sup><sub>liquid</sub>
| ?
|-
| bgcolor="#ffeedd" | S<sup>0</sup><sub>liquid</sub>
| ?
|-
| bgcolor="#ffeedd" | C<sub>p</sub>
| ?
|-
| bgcolor="#ffeedd" | Density
| ?
|-
! bgcolor="#ffddaa" colspan="2" | [[Physics:Gas|Gas]] properties
|-
| bgcolor="#ffeedd" | Δ<sub>f</sub>H<sup>0</sup><sub>gas</sub>
| ?
|-
| bgcolor="#ffeedd" | S<sup>0</sup><sub>gas</sub>
| ?
|-
| bgcolor="#ffeedd" | C<sub>p</sub>
| ?
|- style="border-top: 3px solid gray"
| bgcolor="#ffddaa" colspan="2" align="center" |
<small>
'''Except where noted, all data was produced under conditions of standard temperature and pressure.'''
</small>
|-
|}

Glucose 6-phosphate is [[Chemistry:Glucose|glucose]] sugar phosphorylated on carbon 6. This compound is very common in [[Biology:Cell|cells]] as the vast majority of glucose entering a cell will become phosphorylated in this way.

Because if its prominent position in cellular chemistry, glucose 6-phosphate has many possible fates within the cell. It lies at the start of two major [[Biology:Metabolic pathway|metabolic pathway]]s:
*[[Biology:Glycolysis|Glycolysis]]
*[[Chemistry:Pentose phosphate pathway|Pentose phosphate pathway]]
In addition to these metabolic pathways, glucose 6-phosphate may also be converted to [[Biology:Glycogen|glycogen]] or [[Chemistry:Starch|starch]] for storage. This storage is in the liver in the form of glycogen for most multicellular animals, and in [[Biology:Intracellular|intracellular]] starch or glycogen granules for most other organisms.

==Production of glucose 6-phosphate==

The major reason for the immediate phosphorylation of glucose is to prevent diffusion out of the cell. The phosphorylation adds a charged [[Chemistry:Phosphate|phosphate]] group so the [[Chemistry:Glucose 6-phosphate|glucose 6-phosphate]] cannot easily cross the [[Biology:Cell membrane|cell membrane]], in contrast to free [[Chemistry:Glucose|glucose]].

Within a cell, glucose 6-phosphate is produced by phosphorylation of [[Chemistry:Glucose|glucose]] on the sixth carbon. This is catalyzed by the [[Biology:Enzyme|enzyme]] [[Biology:Hexokinase|hexokinase]] in most cells, and [[Biology:Glucokinase|glucokinase]] in certain cells, most notably liver cells. One [[Biology:Adenosine triphosphate|ATP]] is consumed in this reaction. 

{{Enzymatic Reaction
|foward_enzyme=[[Biology:Hexokinase|Hexokinase]]
|reverse_enzyme=
|substrate=α-<small>D</small>-[[Chemistry:Glucose|Glucose]]
|product=α-<small>D</small>-[[Chemistry:Glucose 6-phosphate|Glucose 6-phosphate]]
|reaction_direction_(foward/reversible/reverse)=foward
|minor_foward_substrate(s)=ATP
|minor_foward_product(s)=ADP
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=Glucose_wpmp.png
|product_image=Glucose-6-phosphate_wpmp.png
}}
{{KEGG compound|C00031}} {{KEGG enzyme|2.7.1.1}} {{KEGG compound|C00668}} {{KEGG reaction|R01786}}

Glucose-6-phosphate is also produced during [[Biology:Glycogenolysis|glycogenolysis]] from glucose-1-phosphate, the first product of the breakdown of [[Biology:Glycogen|glycogen]] polymers.

== Fate 1: Pentose Phosphate Pathway ==
When the ratio of NADP<sup>+</sup> : NADPH increases, the body realizes it needs to produce more NADPH (a reducing agent for several reactions like fatty acid synthesis).  This will cause the G6P to be dehydrogenated by glucose 6-phosphate dehydrogenase.  This reversible reaction is the initial step of the [[Chemistry:Pentose phosphate pathway|pentose phosphate pathway]], which generates the useful cofactor NADPH as well as ribulose 5-phosphate, a carbon source for the synthesis of other molecules .  Also, if the body needs nucleotide precursors of DNA for growth and synthesis, G6P  will also be dehydrogenated and enter the pentose phosphate pathway.

== Fate 2: Glycolysis ==
If the cell needs energy or carbon skeletons for synthesis then glucose 6-phosphate is targeted for [[Biology:Glycolysis|glycolysis]]. Glucose 6-phosphate is first isomerized to fructose-6-phosphate by phosphoglucose isomerase.  

{{Enzymatic Reaction
|foward_enzyme=Phosphoglucose isomerase
|reverse_enzyme=Phosphoglucose isomerase
|substrate=α-<small>D</small>-[[Chemistry:Glucose 6-phosphate|Glucose 6-phosphate]]
|product=β-<small>D</small>-[[Chemistry:Fructose 6-phosphate|Fructose 6-phosphate]]
|reaction_direction_(foward/reversible/reverse)=reversible
|minor_foward_substrate(s)=
|minor_foward_product(s)=
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=Glucose-6-phosphate_wpmp.png
|product_image=Fructose-6-phosphate_wpmp.png
}}
{{KEGG compound|C00668}} {{KEGG enzyme|5.3.1.9}} {{KEGG compound|C05345}} {{KEGG reaction|R00771}}

This reaction converts glucose 6-phosphate to [[Chemistry:Fructose 6-phosphate|fructose 6-phosphate]] in preparation for phosphorylation to Fructose-1,6-bisphosphate.  The addition of the 2<sup>nd</sup> phosphoryl group to produce Fructose-1,6-bisphosphate is an irreversible step, and so is used to irreversibly target the glucose 6-phosphate breakdown to provide energy for ATP production via [[Biology:Glycolysis|glycolysis]].

== Fate 3: Storage as Glycogen ==

Whenever cellular glucose-6-phosphate levels are high the [[Osmotic pressure|osmotic pressure]] inside the cells increases, and this may lead water to diffuse into the cell, causing it to become turgid and (eventually) lyse. Since osmotic pressure is proportional to the concentration of solutes, rather than to the total mass of solutes, this problem can be overcome by storing glucose-6-P in a polymeric form. In plant cells, this polymeric form of glucose is [[Chemistry:Starch|starch]], whereas animals store [[Biology:Glycogen|glycogen]].

== Fate 4: Dephosphorylation and Release into Bloodstream ==
Liver cells possess glucose-6-phosphatase, which removes the phosphate group from glucose-6-phosphate produced during [[Biology:Glycogenolysis|glycogenolysis]] or [[Biology:Gluconeogenesis|gluconeogenesis]]. The free glucose is sent into the bloodstream for uptake by other cells.

== References ==

* {{cite book |last=Berg |first=Jeremy M. |coauthors=Tymoczko, Stryer |title=Biochemistry |year=2002 |edition=5th |publisher=W.H. Freeman and Company |location=New York |id=ISBN 0-7167-3051-0 | url =http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=stryer.TOC&depth=10}}

==See also==
* [[Chemistry:Glucose|Glucose]]
* [[Biology:Glycogen|Glycogen]]
* [[Chemistry:Glucose 1-phosphate|Glucose 1-phosphate]]
* [[Chemistry:Pentose phosphate pathway|Pentose phosphate pathway]]
* [[Chemistry:Starch|Starch]]

==External links==


{{Metabolic pathway}}

[[Category:Organophosphates]][[Category:Monosaccharides]]

{{Sourceattribution|Glucose-6-phosphate|1}}