Diacylglycerol

From Wikipedia, the free encyclopedia

Diacylglycerol (DAG) is a second messenger molecule made by phospholipase C (PLC) (a membrane-bound enzyme), together with inositol triphosphate (IP3). Although inositol triphosphate (IP3) diffuses into the cytosol, diacylglycerol (DAG) stays close to the plasma membrane, due to its hydrophobic properties. IP3 stimulates the release of calcium ions from the smooth endoplasmic reticulum while DAG is still membrane associated and activates protein kinase C (PKC). However, for DAG to activate PKC, there needs to be a cytosolic increase in calcium ions which is one of the functions of IP3.

Diacylglycerol has two major functions in the cell:

as a source for prostaglandins
stimulation of protein kinase C

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

[edit] Synthesis

Diacylglycerol is a pre-cursor to triacylglycerols (triglycerides). Synthesis begins with glycerol-3-phosphate, which is a product of glycolysis (usually in cytoplasm of liver or adipose tissue). Two fatty acid molecules are added to yield phosphatidic acid. Phosphatidic acid is then de-phosphorylated to form diacylglycerol.

Note: Diacylglycerol may form a triacylglycerol with the addition of a third fatty acid molecule.