Cardiolipin synthesis

In eukaryotes, phosphatidylglycerol, cardiolipin, and the phosphatidylinositols (all anionic phospholipids see Fig. 10-8) are synthesized by the same strategy used for phospholipid synthesis in bacteria. Phosphatidylglycerol is made exactly as in bacteria. Cardiolipin synthesis in eukaryotes differs slightly phosphatidylglycerol condenses with CDP-diacylglycerol (Fig. 21-26), not another molecule of phosphatidylglycerol as in E. coli (Fig. 21-25). 

D.B. Ostrander, G.C. Sparagna, A.A. Amoscato, J.B. McMillan, and W. Dow-han. Decreased cardiolipin synthesis corresponds with cytochrome c release in palmitate-induced cardiomyocyte apoptosis, J. Biol. Chem., 2001, 276, 38061-38067. 

Figure 11.14 Phospholipid synthesis in plants. For simplicity the full systematic names for enzymes and co-factor requirements are not given. Details can be found in Mudd (1980). Phosphatidylglycerol is mainly formed in photosynthetic tissues. Methylation pathway to phosphatidylcholine has only been demonstrated in a few plants. Cardiolipin synthesis is probably confined to mitochondria. Other possible sources of diacylglycerol include phospholipase C action, demonstrated in many plants and plant tissues. Reproduced from Harwood and Russell (1984) with permission.

Figure 1. Control of mitochondrial biogenesis by the nuclear genome. Most mitochondrial proteins, including cytochrome c, are nuclear gene products which are subsequently imported into mitochondria. Similarly, most enzymes involved in synthesis of mitochondrial phosphoplipids are encoded in the nuclear genome. Being located in the endoplasmatic reticulum, they synthesize phosphatidylcholine (PtdCho), phosphatidylserine (PtdSer), phosphatidylglycerol (PG) and phosphatidylinositol (Ptdins). The phospholipids are transferred to the outer membrane. The imported lipids then move into the inner membrane at contact sites. Mitochondria then diversify phospholipids. They decarboxylate phosphatidylserine to phosphatidylethanolamine (PtdEtN), but the main reaction is the conversion of imported phosphatidylglycerol to cardiolipin (CL). Cardiolipins localize mainly in the outer leaflet of the inner membrane.

In mammalian cells, the final stage of PS biosynthesis occurs in ER and MAM (Trotter and Voelker, 1994 Daum and Vance, 1997 Voelker, 2000). The other membranes in the ceU, such as mitochondria, nucleus, and plasma membrane, are therefore assembled from PS exported from ER and MAM (Figure 2). Phospholipid synthesis in mitochondria is restricted to the formation ofphosphatidylglycerol, cardiolipin, and PE, and other lipids such as PC and PS must be imported from sites of cellular lipid synthesis, ER or MAM (Daum, 1985 Vance, 1991). PS imported to the outer mitochondrial membrane is then translocated to the inner mitochondrial membrane, where it is converted to PE by PS decarboxylase (PSD) (Dennis and Kennedy, 1972 Voelker, 1990). It has been shown that the translocation of PS to mitochondria followed by its decarboxylation is a major pathway for the synthesis of PE in some cultured mammahan cells (Voelker, 1984 Kuge et al, 1986 Voelker and Frazier, 1986), suggesting that significant amounts of PE found in cell membranes are derived from mitochondria. 

Diphosphatidylglycerol (trivial name cardiolipin) has a unique dimeric structure with four acyl groups and two negative charges (Fig. 1). It is common in bacteria, and it can be found in the iimer mitochondrial membranes of eukaryotes (i.e., those membranes that generate an electrochemical potential for substrate transport and ATP synthesis). 

Cardiolipins (16) occur widely in membranes of subcellular components which display high metabolic activity. However, difficulties in the isolation or synthesis of (16) have hindered studies on structure-function relationships in these compounds. The publication of a synthetic route to (16) is of significance, because specific cardiolipins can now be prepared. One remarkable feature of this synthesis, which makes... 

Subsequent phosphorylations catalyzed by specific kinases lead to the synthesis of pkosphatidylinositol 4,5-bisphosphate, the precursor of two intracellular messengers diacylglycerol and inositol l,4,S-trisphosphate (Section 14.2). If the alcohol is phosphatidylglycerol, the products are diphosphatidylglycerol (cardiolipin) and CMP. In eukaryotes, cardiolipin is located exclusively in inner mitochondrial membranes and plays an important role in the organization of the protein components of oxidative phosphorylation. 

FIGURE 21-26 Synthesis of cardiolipin and phosphatidylinositol in eukaryotes. These glycerophospholipids are synthesized using strategy 1 in Figure 21-24. Phosphatidylglycerol is synthesized as in bacteria (see Fig. 21-25). PI represents phosphatidylinositol. 

Fig. 6. Synthesis of phospholipid polar head groups. The three major phospholipid species in E. coli are synthesized by a total of six different enzymatic activities (1) phosphatidate cytidylyltransferase (Cds), (2) phosphatidylserine synthase (PssA), (3) phosphatidylserine decarboxylase (Psd), (4) phosphatidyl-glycerol phosphate synthase (PgsA), (5) phosphatidylglycerol phosphate phosphatase (PgpA or PgpB), and (6) cardiolipin synthase (els).

CTP phosphatidate cytidylyltransferase has been observed in plastids, mitochondria, and ER. In all three compartments, the CDP-diacylglycerol derived from phosphatidic acid is used in the synthesis of phosphatidylglycerol in mitochondria, the reaction of phosphatidylglycerol with a second CDP-diacylglycerol then produces cardiolipin. The ER can also incorporate CDP-diacylglycerol into phosphatidylinositol and phosphatidylserine. 

Free glycerol is also produced in synthesis of cardiolipin from phosphatidylglycerol (Figure 19.4)... 

Pisch s group [31], Phosphatidylinositol (PI) was synthesized from dioleoyl phosphatidylcholine (DOPC) using mutant PLD [32], although the yield was only 2.5% of PI isomers. While some PLD with plant origins were reported to catalyze PI synthesis, these enzymes were not easily available for industrial purposes [33]. The synthesis of cardiolipin (diphosphatidylglycerol) was also reported by Piazza et al. [34]. 

The literature for peptide-membrane interactions is both vast and well covered. For the purposes of this chapter, we will look only at polymers - molecules made from polymerization reactions rather than solid-state synthesis or extracted from living organisms - made from a- and p-amino acids. Yaroslavov et al examined binding between poly-a-r-lysine (PLL) and anionic vesicles. SUVs of lecithin and cardiolipin were labeled with pyrene and exposed to PLL (Cl6) (Figure 21). The decrease in pyrene fluorescence indicated that PLL binds to the vesicles. Saturable binding was observed. The addition of high concentrations of salt or low... 

Studies with mutant strains of E. coli have demonstrated that there is a connection between the turnover of membrane phospholipids and the synthesis of the so-called membrane-derived oligosaccharides , which are D-gluco-oligo-saccharides variously substituted with sn-glycerol phosphate, ethanolamine phosphate, and succinate on the outer envelope of the cell. The glycerol phosphate residues of these oligosaccharides appear to be donated by phosphatidyl-glycerol or the lipid cardiolipin or both. 

A phosphoramidite approach using 2-cyanoethyl iV,iV-diisopropylchlorophos-phoroamidite was utilized for the first time to synthesize short chain cardiolipins. This approach was extended to the synthesis of long chain esters (47) and their ether analogues. ... 

This structure and its absolute configuration have been confirmed by chemical synthesis (Plackett 1964). By analogy, cardiolipin may also be named diphosphatidyl glycerol. Thus cardiolipin has the following structure ... 

Kiyasu et al. (1963) suggested that in the synthesis of cardiolipin the function of CDP-diglyceride as a donor of phosphatidyl groups might be extended to include the transfer of a phosphatidyl group to phosphatidyl glycerol ... 

In eukaryotic cells, the enzymes responsible for the synthesis of the major phospholipids, occur in the endoplasmic reticulum. Mitochondria, however, can synthesize phosphatidic acid and cardiolipin, a phospholipid present exclusively in mitochondria (Chapter 4). In bacteria, almost all the phospholipid-synthesizing enzymes are localized in the plasma membrane. ... 

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