Biosynthesis Of Phosphatidylglycerol Research Articles

Diphosphatidylglycerol in experimental acute alveolar injury in the dog.

Acute alveolar injury closely resembling that seen in humans was induced in dogs by subcutaneous injection of N-nitroso-N-methylurethane. Necrosis of alveolar epithelial cells was observed during early injury. Proliferation of immature epithelial cells which began during early injury and became massive after peak injury was followed by their differentiation to mature type II cells during recovery. Quantities of diphosphatidylglycerol (DPG) and of phosphatidylglycerol (PG) in alveolar lavage and in post-lavage lung tissue were measured. An increase in tissue DPG coincided with a sharp decrease in tissue and lavage PG during early injury. DPG was not detectable in the lavage. During late recovery, tissue DPG increased threefold over controls. This increase was accompanied by persistence of a 50% decrease in tissue PG and 83% decrease in lavage PG. Biosynthesis of DPG and PG in isolated lung mitochondria demonstrated that DPG was formed from PG in the presence of CDP-diglyceride. These findings suggest that the low level of PG in the surfactant complex during acute alveolar injury is due to increased turnover of PG to DPG in the lung.

Lung surfactant.

Aspects of pulmonary surfactant are reviewed from a biochemical perspective. The major emphasis is on the lipid components of surfactant. Topics reviewed include surfactant composition, cellular and subcellular sites as well as pathways of biosynthesis of phosphatidylcholine, disaturated phosphatidylcholine and phosphatidylglycerol. The surfactant system in the developing fetus and neonate is considered in terms of phospholipid content and composition, rates of precursor incorporation, activities of individual enzymes of phospholipid synthesis and glycogen content and metabolism. The influence of the following hormones and other factors on lung maturation and surfactant production is discussed: glucocorticoids, thyroid hormone, estrogen, prolactin, cyclic AMP, beta-adrenergic and cholinergic agonists, prostaglandins and growth factors. The influence of maternal diabetes, fetal sex, stress and labor are also considered. Nonphysiologic and toxic agents which influence surfactant in the fetus, newborn and adult are reviewed.

Effect of myo-inositol on the glycerophospholipid composition of adult and fetal rat lung tissue.

In many species including man, the second most abundant lipid in lung surfactant is phosphatidylglycerol (PG) which may comprise 10% of the total lipid in surfactant from mature lungs. Infants delivered before their surfactant contained a large amount of PG are at greater risk of succumbing to hyaline membrane disease. Regulation of the PG content of lung surfactant is not understood completely, but the reciprocal changes in the amount of phosphatidylinositol (PI) and PG in surfactant as the lung mature are suggestive of regulation at the level of a common precursor. The immediate common precursor of PI and PG is CDP-diacylglycerol which is found in only small amounts in most mammalian cells and likely restricts the biosynthesis of both PI and PG. It has been observed in several species that the enzymes that synthesize PI and PG compete for the limited amount of CPD-diacylglycerol and this competition is influenced by the availability of myo-inositol. We and others have presented evidence that myo-inositol availability in the developing lung may be an important factor in the regulation of lung surfactant composition. In the present investigation, myo-inositol was administered chronically to nonpregnant and to pregnant rats and the effect of this treatment on the glycerophospholipid composition of lung tissue and lung lavage was measured. In addition, the influence of myo-inositol administration to pregnant rats on the glycerophospholipid composition of lung tissue of their fetuses was investigated. The concentration of myo-inositol in adult and fetal blood was measured by gas-liquid chromatography of its trimethylsilyl derivative. For determination of glycerophospholipid composition, the total lipid extracts of lung tissues and lung lavage were separated by 2-dimensional thin-layer chromatography and quantified by lipid phosphorus assay of individual spots. The concentration of myo-inositol in the serum of pregnant rats was significantly higher than in nonpregnant rats (Tab. I, Fig. 1). Treatment of the rats with myo-inositol resulted in a significant elevation of serum concentrations of myo-inositol throughout the experimental period. Between day 18 and day 21 of the gestation there was a significant decrease in serum myo-inositol concentrations in fetuses of saline treated rats. Treatment of the pregnant dams with myo-inositol resulted in a significant elevation in fetal serum concentrations of myo-inositol on both day 18 and day 21 of gestation (Tab. I).(ABSTRACT TRUNCATED AT 400 WORDS)

Glucosamine-derived phospholipids in Escherichia coli. Structure and chemical modification of a triacyl glucosamine 1-phosphate found in a phosphatidylglycerol-deficient mutant.

Certain Escherichia coli mutants defective in phosphatidylglycerol biosynthesis accumulate novel glucosamine-derived phospholipids. We previously demonstrated that the simplest of these substance (lipid X) is a diacylglucosamine 1-phosphate bearing beta-hydroxymyristoyl groups at positions 2 and 3 (Takayama, K., Qureshi, N., Mascagni, P., Nashed, M. A., Anderson, L., and Raetz, C. R. H. (1983) J. Biol. Chem. 258, 7379-7385). We now report the structural characterization of a triacylglucosamine 1-phosphate (designated lipid Y) that is also found in these mutants. Hydrolyzates of Y contain 2 mol of beta-hydroxymyristate and 1 mol of palmitate/mol of glucosamine. In the lipid, one of the beta-hydroxymyristates is amide-linked at position 2, while the two other fatty acyl groups are ester-linked. Fast atom bombardment mass spectrometry is used to confirm that Y is a monosaccharide derivative and that the molecular weight of Y as the free acid (C50H96NO13P) is 950.29. Analysis of Y by proton NMR spectroscopy at 200 MHz reveals that the anomeric configuration is alpha. Further, one of the esterified fatty acid residues is attached to the 3 OH of the sugar, while the second is linked to an OH moiety of a hydroxymyristate. The 4 and 6 OH groups of the sugar are unsubstituted, as in E. coli lipid X. To establish the precise location of each esterified fatty acyl residue, we subjected Y to a very mild alkaline hydrolysis in the presence of triethylamine. This resulted in the selective removal of a single hydroxymyristoyl group. The triethylamine-treated derivative (lipid Y) has a molecular weight of 723. NMR spectroscopy of Y shows that the 3 OH of the sugar is no longer substituted, while the beta OH of the remaining amide-linked hydroxymyristate is still esterified with palmitate. On the basis of these findings, we propose that lipid Y has the same fundamental structure as lipid X, except for the additional presence of a palmitoyl moiety on the N-linked hydroxymyristate. Presumably, lipid Y is synthesized from X by a selective acylation reaction.

The influence of myo-inositol on phosphatidylglycerol synthesis by rat type II pneumonocytes.

Type II pneumonocytes isolated from adult rat lung were incubated in a serum-free medium containing [14C]glycerol and the incorporation of 14C into glycerophospholipids was measured. After 24 h, more than 80% of the 14C incorporated into total lipids or into phosphatidylcholine and approx. 90% of the 14C incorporated into phosphatidylglycerol after 24 h was recovered in the glycerophosphoester moieties of these molecules. Supplementation of the incubation medium with foetal-bovine serum (10%, v/v) did not alter the incorporation of [14C]glycerol by type II pneumonocytes after 24 h into either a total lipid extract or phosphatidylcholine. In the presence of foetal-bovine serum, however, the incorporation of 14C into phosphatidylglycerol was decreased and the incorporation of 14C into phosphatidylinositol was increased. In the absence of foetal-bovine serum, the incorporation of 14C into phosphatidylglycerol was decreased progressively as the concentration of myo-inositol in the incubation medium was increased. The range of concentration (0.04-0.50 mM) over which myo-inositol had the greatest influence on [14C]glycerol incorporation into phosphatidylglycerol by type II pneumonocytes in vitro encompassed the concentration range measured in foetal-rat serum late in gestation. At 4 days before birth, the concentration of myo-inositol in foetal-rat serum was 0.36 mM and decreased to 0.23 mM 1 day before birth. The concentration of myo-inositol in adult rat serum increased from 0.03 mM to 0.06 mM during pregnancy. Isolated rat type II pneumonocytes were found to take up myo-inositol by a saturable process. A half-maximal rate of myo-inositol uptake occurred at a concentration of myo-inositol of 0.29 mM. The results of this investigation are consistent with the hypothesis that late in gestation there is a decreasing availability of myo-inositol to the foetal lungs and that this favours the biosynthesis of phosphatidylglycerol for surfactant at the expense of phosphatidylinositol biosynthesis.

Development of phosphatidyl glycerol biosynthesis in the lungs of fetuses of diabetic rats

The lungs of fetuses of streptozotocin-diabetic rats were examined for their ability to incorporate U-14C-glucose into phosphatidyl choline, phosphatidyl glycerol, phosphatidyl inositol and lysophosphatidyl choline. In the lungs of control rats an increased biosynthesis of phosphatidyl glycerol in late pregnancy suggested a close association between the production of this phospholipid and the terminal maturation of the fetal lung. In the offspring of diabetic rats the incorporation of 14C-glucose into phosphatidyl choline, lysophosphatidyl choline and phosphatidyl glycerol was markedly decreased compared with the control rats on gestational day 20, whereas no difference was seen at day 22. Insulin treatment of the pregnant rats restored the biosynthesis of phosphatidyl choline and lysophosphatidyl choline towards normal on gestational day 20, while the ratio of phosphatidyl glycerol to phosphatidyl inositol incorporation of 14C-glucose was decreased, suggesting that the biosynthesis of phosphatidyl glycerol is more sensitive than that of phosphatidyl choline and lysophosphatidyl choline to the metabolic disturbances inherent in maternal diabetes. The delayed fetal pulmonary maturation occurred without fetal hyperinsulinism which suggests that this latter feature may not be of crucial significance in the aetiology of the respiratory distress syndrome.

Interaction of CDP-diglyceride spin-label with [formula omitted] B membrane fractions and its relationship with phospholipid synthesis

Interaction of CDP-diglyceride with Escherichia coli B membrane was studied by ESR spectroscopy. The results showed that the micelles of CDP-diglyceride molecules associate with membrane surface in the presence of Mg 2+, whereas, when Mg 2+ was omitted from the system, CDP-diglyceride molecules diffuse rapidly into membrane bilayer. The latter condition was shown to be more preferable for phosphatidylglycerol biosynthesis.

Coordinate increases in the enzyme activities responsible for phosphatidylglycerol synthesis and CTP:cholinephosphate cytidylyltransferase activity in developing rat lung

The enzymes responsible for the biosynthesis of phosphatidylglycerol, CTP:phosphatidate cytidylyltransferase, CDP-diacylglycerol: glycerophosphate phosphatidyltransferase and phosphatidylglycerophosphate phosphatase demonstrated a coordinate increase in activity in fetal rat lung at term when the demand for pulmonary surfactant increases. The activity of CTP:cholinephosphate cytidylyltransferase, the enzyme responsible for CDP-choline production also increased in the perinatal period. The activity of cholinephosphate cytidylyltransferase in fetal and neonatal cytosol was stimulated by the addition of phosphatidylglycerol but no effect was noted with cytosol from adult lung. These results are consistent with the suggestion that the activity of cholinephosphate cytidylyltransferase, a potential rate-determining enzyme in pulmonary phosphatidylcholine synthesis, may be regulated in the perinatal period both through an activation by phosphatidylglycerol and by an increase in total enzyme units.

Synthesis of biologically active spin-labelled radioactive cytidine diphosphodiglyceride, a novel probe for biological membranes

A versatile synthesis of spin-labelled radioactive cytidine diphospho-sn-1,2-diacylglycerol (CDP-diglyceride) has been developed based on the combination of the enzymatic acylation of radioactive sn-glycero-3-phosphate with 12-doxyl stearic acid and the chemical conversion of the thus obtained spin-labelled radioactive phosphatidic acid with cytidine monophosphomorpholi-date into spin-labelled radioactive CDP-diglyceride. The method for the isolation and purification of the latter compound was described. This obtained CDP-[2-3H]diglyceride contained 10% of fatty acids of paramagnetic nature, presumably present as a covalently bound 12-doxyl stearic acid esters. The biological activity was tested by using the synthesized compound as a substrate in the mitochondrial biosynthesis of phosphatidylglycerol. It was found that spin-labelled CDP-[2-3H]diglyceride prepared as described can be converted in the presence of sn-[2-14C]-glycero-3-phosphate into a spin-labelled [2-3H, 2'-14C]phosphatidylglycerol with isolated rat liver mitochondria, establishing therefore that the site of its utilization is identical with the site of phosphatidylglycerol synthesis in isolated mitochondria, i.e. inner mitochondrial membrane. Results described demonstrate that the synthesized spin-labelled CDP-diglyceride can be used as a specific probe for the spin- and radioactive covalent labelling of polyglycerophosphatides of mitochondrial membranes. Some implications and further possibilities in the study of biological membranes using the spin-labelled radioactive CDP-diglyceride are discussed.

Phosphatidylglycerol biosynthesis in Bacillus licheniformis. Resolution of membrane-bound enzymes by affinity chromatography on cytidinediphospho-sn-1,2-diacylglycerol sepharose

Cytidinediphospho-sn-1,2-diaclglycerol (CDP-diglyceride) has been covalently linked to Sephrose 4B via adipic acid dihydrazide spacer arm forming an effective affinity chromatography column. This liponucleo-tide ligand and sn-glycero-3-phosphate are subtracts for the formation of 3-sn-phoshatidyl-1'-sn-glycero-3'-phosphate (PGP) catalyzed in both eukaryotic and prokaryotic organisms by sn-glycero-3-phosphate: CMP phosphatidlytranferase (PGP synthetase). Using this CDP-diglyceride Sephrose affinity column we were able to resolve the membrane associated 3-sn-phosphatidyl'1-sn-glycerol (PG) synthesizing system present in Bacillus licheniformis into two activities. A PGP synthetase activity was adsorbed to the affinity column and was eluted using buffer containg CDP-diglyceride; a PGP phosphatease acactivity had no affinity for the column. Both PGP synthase and PGP phosphatase of B. licheniformis were associated with a membrane component of the cell as evidenced by sucrose gradient centrifugation, differential centrifugation, and solubilization by buffers containing detergent...

Structure and Synthesis of a Lipid‐Containing Bacteriophage

Enzymes of glycerophosphatide biosynthesis and degradation have been characterized using membrane fractions of Pseudomonas BAL‐31, the host cell of the lipid‐containing bacteriophage PM2. Inner and outer membrane fractions were investigated. Whereas the outer membrane con‐tained more phosphatidylethanolamine and less phosphatidylglycerol than the inner membrane, the fatty acid composition was almost the same for both membranes. The pathway for glycerophos‐phatide biosynthesis was the same as that for Escherichia coli and Bacillus megaterium. The biosyn‐thesis of phosphatidylserine and phosphatidylglycerol was shown to proceed via CDP‐diglyceride as a common intermediate. Phospholipase A hydrolyzed phosphatidylethanolamine more efficiently than phosphatidylglycerol. All of the enzymatic activities were stimulated by Triton X‐100. Phos‐phatidylserine synthetase was stimulated by Na2SO4 and inhibited by Mg2+. Phosphatidylserine decarboxylase was completely inhibited by NH2OH. Phosphatidylglyceror synthetase was stimulated by Mg2+. Phospholipase A was stimulated by Ca2+. Phosphatidylserine decarboxylase and phosphatidylglycerol synthetase were localized in the inner membrane fraction. Phosphatidylserine synthetase and phospholipase A were found in both outer and inner membrane fractions.Effects of virus infection on these enzymes were studied. Phosphatidylglycerol synthetase and phospholipase A activity against phosphatidylethanolamine were activated early post‐infection. Phosphatidylserine synthetase and decarboxylase remained unaltered. At later times post‐infection, phosphatidylglycerol synthetase and phosphatidylserine decarboxylase were inactivated and phos‐ phatidylserine synthetase was activated. There was little alteration in phospholipase A activity against phosphatidylglycerol after infection.

Role of lamellar inclusions in surfactant production: studies on phospholipid composition and biosynthesis in rat and rabbit lung subcellular fractions.

Lamellar inclusion bodies in the type II alveolar epithelial cell are believed to be involved in pulmonary surfactant production. However, it is not clear whether their role is that of synthesis, storage, or secretion. We have examined the phospholipid composition and fatty acid content of rabbit lung wash, lamellar bodies, mitochondria, and microsomes. Phosphatidylcholine and phosphatidylglycerol, the surface-active components of pulmonary surfactant, accounted for over 80% of the total phospholipid in lung wash and lamellar bodies but for only about 50% in mitochondria and microsomes. Phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin accounted for over 40% of the total in mitochondria and microsomes but for only 6% in lung wash and 15% in lamellar bodies. The fatty acid composition of lamellar body phosphatidylcholine was similar to that of lung wash, but different from that of mitochondria and microsomes, in containing palmitic acid as a major component with little stearic acid and few fatty acids of chain length greater than 18 carbon atoms. The biosynthesis of phosphatidylcholine and phosphatidylglycerol was examined in the mitochondrial, microsomal, and lamellar body fractions from rat lung. Cholinephosphotransferase was largely microsomal. The activity in the lamellar body fraction could be attributed to microsomal contamination. The activity of glycerolphosphate phosphatidyltransferase, however, was high in the lamellar body fraction, although it was highest in the mitochondria and was also active in the microsomes. These data suggest that the lamellar bodies are involved both in the storage of the lipid components of surfactant and in the synthesis of at least one of those components, phosphatidylglycerol.

Identification of cytidine diphosphate-diglyceride in the pineal gland of the rat and its accumulation in the presence of DL-propranolol.

CDP-diglyceride, an important metabolic intermediate in the biosynthesis of phospholipids, has been isolated for the first time from a mammalian tissue. The isolated material, labeled in incubations of intact rat pineal glands with 32P, [3H]cytidine, or [3H]CTP in the presence of DL-propranolol, was chromatographically identical with authentic CDP-diglyceride and was able to serve as phosphatidyl donor in the enzymatic synthesis of phosphatidylinositol and phosphatidyglycerol. It yielded the expected products upon enzymatic and chemical degradation. No dCDP-diglyceride was detected No radioactive CDP-diglyceride was detected following incubations in the absence of propranolol. Stimulation of CDP-diglyceride labeling from 32P1 occurred at propranolol concentrations between 0.03 and 1.0 mM. Net synthesis of the liponucleotide was shown. At 0.1 mM, propranolol incrased the incorporation of radioactivity into phosphatidylglycerol, phosphatidylinositol, and phosphatidic acid. When inositol (10 mM) and propranolol (0.1 mM) were both present, phosphatidylinositol labeling was further increased, wheas stimulation of phosphatidylglycerol and CPD-diglyceride labeling was abolished. Since CDP-diglyceride did not accumulate in the absence of the drug, its availability may normally be the limiting factor in phosphatidylinositol and phosphatidylglycerol biosynthesis. When propranol is present, inositol may become limiting and thus may lead to the observed labeling pattern.

Biochemistry of polyglycerophosphatides. Effect of divalent cations on the biosynthesis and composition of polyglycerophosphatides in isolated mitochondria.

The effect of the addition of divalent cations on the formation of phosphatidylglycerophosphate, phosphatidylglycerol, and cardiolipin in isolated mitochondria from rat liver and guinea pig heart was studied. Although it was confirmed that the biosynthesis of phosphatidylglycerol in rat liver mitochondria does not require the addition of divalent cations, the addition of Mn2+ and Mg2+ has a profound effect on the level of synthesis and composition of polyglycerophosphatides. By developing a method for the preparation of membrane-bound labeled phosphatidylglycerol and an assay for the quantitative determination of polyglycerophosphatides, the high conversion of phosphatidylglycerol-2′-3H to cardiolipin-3H was established only in the presence of Mn2+ and/or Mg2+. Zn2+ and Ca2+, in the concentration tested, did not stimulate this conversion, nor were they inhibitory. In addition, the association of formed cardiolipin-3H with the mitochondrial membrane was demonstrated. Some implications of these findings are discussed.

Biosynthesis of phosphatidylglycerol by cell-free preparations from spinach leaves

1. 1. An enzyme system in spinach leaf cell-free preparations was found to catalyze the formation of phosphatidylglycerol from CDP-diglyceride and s n-[1,3- 14C]-glycerol 3-phosphate. 2. 2. From the distribution of marker enzymes in subcellular fractions, the system was found to be localized largely in the microsomal fraction. 3. 3. The microsomal enzyme system required Mg 2+ or Mn 2+ as co-factors and was not inhibited by sulphydryl reagents. 4. 4. Experiments using 14C and 32P doubly labelled glycerophosphate provided evidence that phosphatidylglycerol in leaves is biosynthesized via the intermediate formation of phosphatidyl glycerophosphate by the same pathway as in animal tissues and bacteria.

Biosynthesis of phosphatidylglycerol during greening of synchronous dark-grown Euglena gracilis Z

Biosynthesis of phosphatidylglycerol during greening of synchronous dark-grown Euglena gracilis Z

Studies on the Membranes of Bacilli: I. PHOSPHOLIPID BIOSYNTHESIS

Abstract Ghosts of a Bacillus sp. isolated from a culture of Bacillus megaterium KM were prepared by the lysozyme technique and found to be free of several typical cytoplasmic and cell wall components. All of the enzymes responsible for the synthesis of phosphatidylethanolamine and phosphatidylglycerol from phosphatidic acid were found to be present in the ghosts. The biosynthesis of phosphatidylethanolamine and phosphatidylglycerol was shown to proceed via CDP-diglyceride as a common intermediate. When synthesized in vitro this intermediate, as well as the end products, were found to be associated with the ghosts. In studies of the properties of the individual enzymes, it was found that all of the enzymatic activities were stimulated by addition of Mg++ and a nonionic detergent, and had similar pH optima.

An examination of the relation between endogenous lipid and the activity of the phosphatidylglycerol-forming enzyme system in beef heart mitochondria and microsomes.

The effect of endogenous lipid on the biosynthesis of phosphatidylglycerol in beef heart mitochondria and microsomes has been studied by assaying the CDP-D-diglyceride-dependent conversion of L-glycero-3-phosphate-2-3H to phosphatidylglycerol. It was found that lipid-depleted (by wafer–acetone–ammonia treatment) subcellular particles retained in mitochondria 30% and in microsomes 71% of the original activity found in lipid-containing subcellular particles. Mitochondria extracted with ether for a prolonged time (20 min) lost all activity, while mitochondria treated with water–acetone (but without ammonia) still retained 61% of the phosphatidylglycerol-forming activity. The loss of activity was found to be irreparable either by the addition of extracted endogenous lipid of subcellular particles, or by the addition of chemically well-defined lipids. Some implications of the experimental findings concerning the possible role of endogenous lipid in the activity of the enzyme system catalyzing the formation of phosphatidylglycerol in subcellular particles are discussed.

Effect of testosterone on the biosynthesis of phosphatidylglycerol from L-alpha-glycerophosphate-2-3H by whole homogenate and mitochondria from rat ventral prostate.

The formation of labeled phosphatidylglycerol from L-α-glycerophosphate-2-3H and CDP-D-diglyceride has been demonstrated in homogenate and mitochondria isolated from rat ventral prostate. In addition, labeled phosphatidylglycerophosphate was detected as a minor biosynthesized lipid. Homogenates and mitochondria isolated from prostates after castration of rats have a decreased ability to incorporate L-α-glycerophosphate-2-3H and CDP-D-diglyceride into phospholipids, but this ability is restored after the administration of testosterone to the castrated animals. The composition of synthesized phospholipids by homogenates and mitochondria isolated from normal and sham-operated rats, and from normal and castrated rats treated with testosterone, is very similar; the major labeled lipid (ca. 90%) being phosphatidylglycerol. This composition is very different when mitochondria isolated from prostates of castrated rats were incubated with the same substrates: labeled phosphatidylglycerol (ca. 55-58%) and phosphati...

Biochemistry of polyglycerophosphatides in central nervous tissue. I. On the biosynthesis, structure, and enzymatic degradation of phosphatidylglycerophosphate and phosphatidylglycerol in isolated sheep brain mitochondria

The formation of labelled phosphatidylglycerophosphate and phosphatidylglycerol from L-glycero-3-phosphate-2-3H and cytidine diphosphate (CDP)-D-diglyceride in subcellular particles of sheep brain has been studied, establishing the predominant location of this enzyme system in mitochondria. The general characteristics and the optimal conditions for the biosynthesis of these lipids have been determined and the chromatographic separation and isolation of phosphatidylglycerophosphate and phosphatidylglycerol are described. In addition, the chemical and enzymatic degradations supporting the structure and configuration for each biosynthesized lipid are presented. The enzymatic dephosphorylation of phosphatiadylglycerophosphate to phosphatidylglycerol with mitochondria isolated from sheep brain has been found. No biosynthesized cardiolipin was, however, detected.The mechanism of the enzymatic reactions for the formation of these lipids has been studied by using L-glycero-3-phosphate[33P]-2-3H and CDP-D-diglyceride; the pathway found by Kennedy et al. (1) for the biosynthesis of phosphatidylglycerol in liver is applicable in the biosynthesis of this compound in sheep brain mitochondria.