The incorporation of [14C]acetate into the constituent fatty acids of monogalactosyldiglyceride by isolated spinach chloroplasts

McKee, Joseph W.A.; Hawke, J. C.

doi:10.1016/0003-9861(79)90252-2

Cited by 34 publications

(31 citation statements)

References 33 publications

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“…4b). This property is in complete agreement with results from in vivo labeling experiments, where, after short label- ing times, oleate was found at C-and palmitate at C-2 of typical chloroplast lipids (14,16,22,26,27).…”

Section: Resultssupporting

confidence: 90%

“…When these analyses were extended to labeled lipids from leaves or chloroplasts of 16:3-plants, common patterns were observed in all chloroplast lipids. After short labeling times, they carried mainly oleate at C-I and palmitate at C-2 (16,22,26,27), which suggests a common diacylglycerol precursor. The only exception in chloroplasts is phosphatidyl choline, which carries palmitate esterified at the C-1 position.…”

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confidence: 94%

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Positional Specificity and Fatty Acid Selectivity of Purified sn-Glycerol 3-Phosphate Acyltransferases from Chloroplasts

Bertrams¹,

Heinz²

1981

Plant Physiol.

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Soluble acyl-CoAsn-glycerol 3-phosphate acyltransferases (EC 23.1.15) which are localized in chloroplasts were purified from leaves of Pisum sativum and Spinacia oke.aca and obtained free from interfering activities. The purification raised the specific activities by factors of about 1,000 for pea and 200 for spinach preparations. In pea chloroplasts, acyltransferase activity occurs in two soluble forms with apparent isoelectric points of 6.3 and 6.6. For both forms, the same molecular weight of about 42,000 was determined. The enzyme from spinach chloroplasts showed a slightly higher molecular weight and a lower isoelectric point of 5.2.The enriched enzyme fractions possessed a specificity for glycerol 3-phosphate as acyl acceptor and did not use dihydroxyacetone phosphate. Besides acyl-CoA, acyl-acyl carrier protein also can function as acyl donor. With acyl-CoA as acyl donor, the enzyme shows a high positional specificity, since the predominant product is 1-acylglycerol 3-phosphate.Different acyl-CoAs, when offered separately, were all accepted as substrates, whereas incubations with mixtures of palmitoyl-, stearoyl-, and oleoyl-CoA demonstrated a preference for olec acid. The acyltransferase from spinach displays higher selectivity than does the enzyme from pea and, therefore, may be responsible for the preferred esterification of oleic acid at the C-1 position in chloroplast lipids and the exclusion of palmitic acid from this position as observed during in vivo labeling experiments.When membrane lipids contain different fatty acids, they are usually distributed asymmetrically between positions C-1 and C-2 of the glycerol backbone. In leaf lipids, palmitic acid and unsaturated C18-fatty acids such as linoleic and linolenic acid predominate. In so-called 16:3-plants, in addition to linolenic acid, the lower homologue hexadecatrienoic acid is present and accumulates specifically in monogalactosyl diacylglycerol (13). Positional analyses have shown that this acid is confined to C-2 in this glycolipid, whereas linolenic acid is found in both positions (12). When these analyses were extended to labeled lipids from leaves or chloroplasts of 16:3-plants, common patterns were observed in all chloroplast lipids. After short labeling times, they carried mainly oleate at C-I and palmitate at C-2 (16,22,26,27), which suggests a common diacylglycerol precursor. The only exception in chloroplasts is phosphatidyl choline, which carries palmitate esterified at the C-1 position.The discovery that, apart from other organelles also chloroplasts (3, 15) contain acyl-CoA:glycerol 3-P acyltransferase activity suggested that this enzyme may be involved in the control of fatty acid distribution in chloroplast lipids, since it catalyzes the first acylation step in the de novo synthesis ofcomplex lipids. Therefore, we purified this chloroplast enzyme to investigate its general 'This work was supported by the Deutsche Forschungsgemeinschaft.properties as well as its positional and fatty acid specificity. The results show tha...

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Section: Resultssupporting

confidence: 90%

mentioning

confidence: 94%

Positional Specificity and Fatty Acid Selectivity of Purified sn-Glycerol 3-Phosphate Acyltransferases from Chloroplasts

Bertrams¹,

Heinz²

1981

Plant Physiol.

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“…Even though further desaturation at both positions of Solanum MGD had produced a complex pattern, it had the same procaryotic pattern as shown by reversed-phase TLC (see below), since no C 18 chains were found at C-2. Previous studies with isolated spinach chloroplasts (14,18,20) resulted in the same distributions as those shown in Figure 3.…”

supporting

confidence: 73%

“…MGD of a similar fatty acid composition as shown in Figure 2 for peas was recently found to be synthesized in an independent study of pea chloroplasts (4) and by the combined action of the two acyltransferases in a reconstituted system from pea chloroplasts (5). Isolated spinach chloroplasts produced similar profiles of labeled fatty acids in various intermediates (14,18,20). In summary, the analysis of fatty acid composition does not reveal differences with regard to the fatty acids formed or incorporated during short-term incubations into lipids by 16:3 and 18:3 chloroplasts, since all DAG-containing lipids have about equal proportions of saturated and monoenoic acids.…”

mentioning

confidence: 79%

“…The C-l position is occupied by C 18 fatty acids and to a small extent by C16 groups. The similarity in DAG backbones of lipids from blue-green algae (22, 30) with those synthesized by the chloroplast-confmed pathway in 16:3 plants suggests a phylogenetic relation and justifies the term procaryotic.The different pathways just mentioned were deduced from labeling experiments with leaves from a small selection of 18:3 and 16:3 plants (17,24,26,29), whereas studies with isolated chloroplasts were mainly confined to organelles from the 16:3 plant spinach (14,20). To provide additional evidence for the roles ascribed to chloroplasts in pro-or eucaryotic pathways during MGD biosynthesis in different plants, we carried out experiments with chloroplasts isolated from 18:3 as well as 16:3 plants.…”

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Similarities and Differences in Lipid Metabolism of Chloroplasts Isolated from 18:3 and 16:3 Plants

Heinz¹,

Roughan²

1983

Plant Physiol.

261

167

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Photosynthetically active chloroplasts reting high rates of fatty acid synthesis from i1-"4Clacetate were purifie from leaves of both 16:3 (Solaum nodiforuu, Chenopodiwm album) and 183 plants (Amaranthu lividus, Pisum sativum). A comparson of lipids into which newly synthesized fatty acids were incorporated revealed that, in 183 chloroplasts, enzymic activities catalyzing the conversion of phosphatidate to diacylglycerol and of diacyiglycerol to monogalactosyl diacylglycerol (MGD) were significantiy less active than in 16:3 chloroplasts. In contrast, labeling rates of MGD from UDP-I14Cigal were similar for both types of chloroplasts. having two linoleoyl groups results in an accordingly unsaturated MGD. The MGD-linked acyl groups are substrates for the introduction of the third double bonds (16) to yield MGD with two linolenoyl residues. This galactolipid is characteristic of 18:3 plants such as Asteraceae and Fabaceae, for example (9). It is called eucaryotic MGD, because the nucleocytoplasmic part of the cell controls the construction of the DAG backbone which carries C 18 fatty acids at both C-1 and C-2 positions of glycerol (7), whereas C 16:0, if present, is excluded from C-2.In photosynthetically active cells of 16:3 plants which are represented, for example, by members of Apiaceae and Brassicaceae (9), two pathways operate in parallel (18) to provide thylakoids with MGD. The cooperative 'eucaryotic' sequence (4) is supplemented to various extents by a 'procaryotic' pathway. Its reactions are confined to the chloroplast and result in a typical arrangement of acyl groups as well as their complete desaturation once they are esterified to MGD. Procaryotic DAG backbones carry C 16:0 and its desaturation products at C-2 (7) from which position C18: fatty acids are excluded. The C-l position is occupied by C 18 fatty acids and to a small extent by C16 groups. The similarity in DAG backbones of lipids from blue-green algae (22, 30) with those synthesized by the chloroplast-confmed pathway in 16:3 plants suggests a phylogenetic relation and justifies the term procaryotic.The different pathways just mentioned were deduced from labeling experiments with leaves from a small selection of 18:3 and 16:3 plants (17,24,26,29), whereas studies with isolated chloroplasts were mainly confined to organelles from the 16:3 plant spinach (14,20). To provide additional evidence for the roles ascribed to chloroplasts in pro-or eucaryotic pathways during MGD biosynthesis in different plants, we carried out experiments with chloroplasts isolated from 18:3 as well as 16:3 plants. Our data suggest that chloroplasts from these two groups of plants have similarities and differences in enzymic equipment explaining some of the above mentioned complications in lipid biosynthesis. Chloroplast Isolation. The medium (12) used for isolating chloroplasts, forming gradients, measuring O2 evolution and lipid synthesis contained 25 mm Hepes, 10 mm KHCO3, 2 mm EDTA, 1 mM MgCl2, 1 mm MnCl2, 0.3 mm KH2PO4, and 0.33 M sorbitol, adjusted to ...

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On the Control of Fatty Acid Compositions of Plant Glycerolipids

Roughan¹

1987

The Metabolism, Structure, and Function of Plant Lipids

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The incorporation of [14C]acetate into the constituent fatty acids of monogalactosyldiglyceride by isolated spinach chloroplasts

Cited by 34 publications

References 33 publications

Positional Specificity and Fatty Acid Selectivity of Purified sn-Glycerol 3-Phosphate Acyltransferases from Chloroplasts

Positional Specificity and Fatty Acid Selectivity of Purified sn-Glycerol 3-Phosphate Acyltransferases from Chloroplasts

Similarities and Differences in Lipid Metabolism of Chloroplasts Isolated from 18:3 and 16:3 Plants

On the Control of Fatty Acid Compositions of Plant Glycerolipids

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