Diglyceride
4239811
217817427
2008-06-07T20:37:45Z
128.23.142.192
/* PKC activation */
[[Image:DAGv1.png|thumb|right|250px|1-Palmitoyl-2-oleoyl-glycerol]]
A '''diglyceride''', or a '''diacylglycerol''' (DAG), is a [[glyceride]] consisting of two [[fatty acid]] chains [[covalent bond|covalently bonded]] to a [[glycerol]] molecule through [[ester]] linkages.
One example, shown on the right, is 1-palmitoyl-2-oleoyl-glycerol, which contains side-chains derived from [[palmitic acid]] and [[oleic acid]]. Diacylglycerols can also have many different combinations of fatty acids attached at both the C-1 and C-2 positions.
== Food additive ==
Mono- and diacylglycerols are common food additives used to blend together certain ingredients, such as oil and water, which would not otherwise blend well.
The commercial source may be either animal (cow- or hog-derived) or vegetable, derived primarily from soy bean and canola oil. They may also be synthetically produced. They are often found in bakery products, beverages, ice cream, chewing gum, shortening, whipped toppings, margarine, and confections.
== Biological functions ==
===PKC activation===
In biochemical signaling, diacylglycerol functions as a [[second messenger]] [[lipid signaling|signaling lipid]], and is a product of the hydrolysis of the phospholipid [[PIP2]] (phosphatidyl inositol-bisphosphate) by the enzyme [[phospholipase]] C (PLC) (a [[cell membrane|membrane]]-bound [[enzyme]]) that, through the same reaction, produces [[inositol triphosphate]] (IP<sub>3</sub>). Although inositol triphosphate (IP<sub>3</sub>) diffuses into the [[cytosol]], diacylglycerol (DAG) remains within the [[plasma membrane]], due to its [[hydrophobe|hydrophobic]] properties. IP<sub>3</sub> stimulates the release of calcium ions from the smooth endoplasmic reticulum, whereas DAG is a physiological activator of [[protein kinase C]] (PKC). The production of DAG in the membrane facilitates translocation of PKC from the cytosol to the [[plasma membrane]].
Diacylglycerol can be mimicked by the tumor-promoting compounds [[phorbol esters]].
=== Other===
In addition to activating PKC, diacylglycerol has a number of other functions in the [[cell (biology)|cell]]:
* a source for [[prostaglandin]]s
* a precursor of the [[endocannabinoid]] [[2-arachidonoylglycerol]]
* an activator of a subfamily of [[TRPC]] ('''T'''ransient '''R'''eceptor '''P'''otential '''C'''anonical) cation channels, TRPC3/6/7.
== Metabolism ==
Synthesis of diacylglycerol begins with [[glycerol-3-phosphate]], which is derived primarily from [[dihydroxyacetone phosphate]], a product of [[glycolysis]] (usually in the cytoplasm of liver or adipose tissue cells). Glycerol-3-phosphate is first [[acylation|acylated]] with acyl-coenzyme A (acyl-CoA) to form [[lysophosphatidic acid]], which is then acylated with another molecule of acyl-CoA to yield [[phosphatidic acid]]. Phosphatidic acid is then de-phosphorylated to form diacylglycerol.
Diacylglycerol is a precursor to [[triacylglycerol]] (triglyceride), which is formed in the addition of a third fatty acid to the diacylglycerol under the catalysis of [[diglyceride acyltransferase]].
Since diacylglycerol is synthesized via phosphatidic acid, it will usually contain a saturated fatty acid at the C-1 position on the glycerol moiety and an unsaturated fatty acid at the C-2 position. <ref name=Stryer_2006>{{cite book | author = Berg J, Tymoczko JL, Stryer L | title = Biochemistry | publisher = W. H. Freeman | edition = 6th ed. | location = San Francisco | year = 2006 | isbn = 0716787245 }}</ref>
==Additional images==
<gallery>
Image:PIP2 cleavage to IP3 and DAG.jpg|PIP2 cleavage to IP3 and DAG initiates intracellular calcium release and PKC activation.
</gallery>
==References==
{{Reflist}}
{{Glycerides}}
{{Lipid_signaling}}
[[Category:Lipids]]
[[Category:Carboxylate esters]]
[[Category:Signal transduction]]
[[da:Diglycerid]]
[[de:Diacylglycerol]]
[[es:Diacilglicerol]]
[[he:דיגליצריד]]
[[ja:ジアシルグリセロール]]
[[pl:Diacyloglicerole]]
[[ur:دو ایسائل گلسرول]]