Cardiolipins

Cardiolipins Cardiolipin (CL) is made up of two phosphatidyl moieties linked by a glycerol bridge. It is a tetra-acylated glycerophospholipid playing a crucial role in in both prokaryotic and eukaryotic cells. It is located at membranes associated with the production of an electrochemical gradient assisted in the production of ATP and the transportation of substrates across the cell membrane. CL is abundant in mitochondria of eukaryotic cells, especially the inner membrane of mitochondria. It is necessary for efficient transport of electrons across cytochrome c oxidase by binding this enzyme tightly. Besides, it is also related to the function ATP synthase, the cytochrome bc1 complex and ATP/ADP exchange protein the F0F1. By taking part in cytochrome c release from the mitochondria, CL may play an important role in apoptosis.

• Cardiolipin is composed 4 acyl chains and can be acylated with a large number of different acyl chains. Because of this kind of structure, there is a staggering number of possible CL molecular species. With more than 10 different kinds of acyl chains randomly distributed among the four esters, there are more than 104 distinct possible CL molecular structures. One type of cell may not include all of these possible cardiolipins. Depend on the organism, organ, and cell type, the acyl chain composition of cardiolipins may be different and specific. Any changes of the composition or the acylation state of CL would lead to the dysfunction of the mitochondria. These dysfunction are involved in a series of disorders like aging, as ischemia, hypothyroidism and heart failure.

• Cardiolipin is synthesized in a pathway similar to other glycerophospholipids. The acylation of glycerol 3-phosphate leads to the generation of phosphatidic acid, which in turn is being activated to CDP-diacylglycerol (CDP-DAG). CDP- DAG reacts within a second glycerol 3-phosphate and produces phosphatidylglycerol phosphate. The phosphate was removed from the terminal glycerol by a phosphatase and produce phosphatidylglycerol. The biosynthetic pathways of cardiolipin in prokaryotic and eukaryotic cells converge at this point. The final step for the formation of CL in prokaryotes and eukaryotes is different. In eukaryotes, a second CDP-diacylglycerol molecule reacts with phosphatidylglycerol and generates CL and CMP is released at the same time. In prokaryotes, CL is generated by two phosphatidylglycerol molecules and free glycerol is released at the same time.

• Creative Proteomic developed a method for the quantification of CL molecular species by LC-MS/MS. The CLs are identified by their total number of carbons and unsaturations in the acyl chain composition. This method can’t determine the exact molecular structure of the CL. By adding CL standards, cardiolipins concentrations in biological samples are quantified with high sensitivity and reliability.