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Chemical structure of the diglyceride 1-palmitoyl-2-oleoyl-glycerol

A di-glyceride, or a diacyl-glycerol (DAG), is a glyceride consisting of two fatty acid chains 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 other combinations of fatty acids attached at either the C-1 and C-2 positions or the C-1 and C-3 positions.

Food additive

Diglycerides, generally in a mix with monoglycerides (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]}.

The commercial source may be animal fat, commonly derived from cattle, hogs or other livestock, depending on the region. It also may be derived from vegetable fat, such as soy bean or canola oil, possibly hydrogenated, depending on requirements and available supplies.^{[citation needed]} Conversely, they also may be synthetically produced. They often are included in bakery products, beverages, ice cream, peanut butter, chewing gum, shortening, whipped toppings, margarine, confections, and candies.

Biological functions

Protein kinase C activation

PIP2 cleavage to IP3 and DAG initiates intracellular calcium release and PKC activation.

In biochemical signaling, diacylglycerol functions as a second messenger signaling lipid, and is a product of the hydrolysis of the phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2) by the enzyme phospholipase C (PLC) (a membrane-bound enzyme) that, through the same reaction, produces inositol trisphosphate (IP₃). Although inositol trisphosphate diffuses into the cytosol, diacylglycerol remains within the plasma membrane, due to its hydrophobic properties. IP₃ 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.^[1]

Other

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

a source for prostaglandins
a precursor of the endocannabinoid 2-arachidonoylglycerol
an activator of a subfamily of transient receptor potential canonical (TRPC) cation channels, TRPC3/6/7.

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.

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.^[2]

Diacylglycerol can be phosphorylated to phosphatidic acid by diacylglycerol kinase.

References

^ Blumberg, Peter M. (1988). "Protein Kinase C as the Receptor for the Phorbol Ester Tumor Promoters: Sixth Rhoads Memorial Award Lecture". Cancer Research 48 (1): 1–8. PMID 3275491.
^ Berg J, Tymoczko JL, Stryer L (2006). Biochemistry (6th ed.). San Francisco: W. H. Freeman. ISBN 0-7167-8724-5. ^{[page needed]}

English Journal

Production of novel "functional oil" rich in diglycerides and phytosterol esters with "one-pot" enzymatic transesterification.

Zheng MM1, Huang Q, Huang FH, Guo PM, Xiang X, Deng QC, Li WL, Wan CY, Zheng C.
Journal of agricultural and food chemistry.J Agric Food Chem.2014 Jun 4;62(22):5142-8. doi: 10.1021/jf500744n. Epub 2014 May 22.
Diglycerides and phytosterol esters are two important functional lipids. Phytosterol esters mixed with dietary diglyceride could not only influence body weight but also prevent or reverse insulin resistance and hyperlipidemia. In this study, a kind of novel "functional oil" rich in both diglycerides
PMID 24815553

A functional polyester carrying free hydroxyl groups promotes the mineralization of osteoblast and human mesenchymal stem cell extracellular matrix.

Bi X1, You Z2, Gao J3, Fan X4, Wang Y5.
Acta biomaterialia.Acta Biomater.2014 Jun;10(6):2814-23. doi: 10.1016/j.actbio.2014.02.018. Epub 2014 Feb 18.
Functional groups can control biointerfaces and provide a simple way to make therapeutic materials. We recently reported the design and synthesis of poly(sebacoyl diglyceride) (PSeD) carrying a free hydroxyl group in its repeating unit. This paper examines the use of this polymer to promote biominer
PMID 24560799

Adipose triglyceride lipase activity is inhibited by long-chain acyl-coenzyme A.

Nagy HM1, Paar M1, Heier C1, Moustafa T1, Hofer P1, Haemmerle G1, Lass A1, Zechner R1, Oberer M1, Zimmermann R2.
Biochimica et biophysica acta.Biochim Biophys Acta.2014 Apr 4;1841(4):588-94. doi: 10.1016/j.bbalip.2014.01.005. Epub 2014 Jan 16.
Adipose triglyceride lipase (ATGL) is required for efficient mobilization of triglyceride (TG) stores in adipose tissue and non-adipose tissues. Therefore, ATGL strongly determines the availability of fatty acids for metabolic reactions. ATGL activity is regulated by a complex network of lipolytic a
PMID 24440819

Japanese Journal

A Simple Engineering Technique to Improve Transesterification for Biodiesel Fuel Production

HAYASHI Tomoki,HABAKI Hiroaki,EGASHIRA Ryuichi
Journal of chemical engineering of Japan 46(4), 461-466, 2013-07-01
… The constant for the conversion of triglyceride to diglyceride was the smallest. …
NAID 10031188019

アスリートのための機能性食品、飲料および成分

Spano Marie
Strength & conditioning journal : 日本ストレングス&コンディショニング協会機関誌 20(2), 57-62, 2013-03
NAID 40019599432

Phase Behavior, Functions, and Medical Applications of Soy Phosphatidylcholine and Diglyceride Lipid Compositions

TIBERG Fredrik,JOHNSSON Markus,JANKUNEC Marija,BARAUSKAS Justas
Chemistry letters 41(10), 1090-1092, 2012-10-05
… This is shown in detail for the binary phosphatidylcholine and diglyceride lipid systems, which are currently being used in multiple programs for the development of novel pharmaceuticals and marketed products. …
NAID 10031120591