Diglyceride

Source: Wikipedia, the free encyclopedia.
General chemical structures of 1,2-diacylglycerols (top) and 1,3-diacylglycerols (bottom), where R1 and R2 are fatty acid side chains

A diglyceride, or diacylglycerol (DAG), is a

emulsifiers in processed foods. DAG-enriched oil (particularly 1,3-DAG) has been investigated extensively as a fat substitute due to its ability to suppress the accumulation of body fat;[3][4] with total annual sales of approximately USD 200 million in Japan since its introduction in the late 1990s till 2009.[3]

Production

Diglycerides are a minor component of many

triglycerides and glycerol. The raw materials for this may be either vegetable oils or animal fats.[6]

Food additive

Diglycerides, generally in a mix with

E471), are common food additives largely used as emulsifiers. The values given in the nutritional labels for total fat, saturated fat, and trans fat do not include those present in mono- and diglycerides.[citation needed] They often are included in bakery products, beverages, ice cream, peanut butter, chewing gum, shortening, whipped toppings, margarine, confections, and some snack products, such as Pringles
.

Biological functions

Protein kinase C activation

PIP2 cleavage to IP3 and DAG initiates intracellular calcium release and PKC activation. Note: PLC is not an intermediate like the image may confuse, it actually catalyzes the IP3/DAG separation

In biochemical signaling, diacylglycerol functions as a

plasma membrane
.

Munc13 activation

Diacylglycerol has been shown to exert some of its excitatory actions on vesicle release through interactions with the presynaptic priming protein family Munc13. Binding of DAG to the C1 domain of Munc13 increases the fusion competence of synaptic vesicles resulting in potentiated release.

Diacylglycerol can be mimicked by the tumor-promoting compounds phorbol esters.[7]

Other

In addition to activating PKC, diacylglycerol has a number of other functions in the cell:

Metabolism

glycerol-3-phosphate

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 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.

Dietary fat is mainly composed of

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.[8]

Diacylglycerol can be phosphorylated to phosphatidic acid by diacylglycerol kinase.

Insulin resistance

Activation of

IRS1-associated PI3K activity.[9] Similarly, activation of PKCε by diacyglycerol may cause insulin resistance in the liver.[9][10]

See also

References