Abstract
Triacylglycerols of both Tropaeolum majus L. and Limnanthes douglasii R. Br. are predominantly esterified with very long-chain acyl groups at each position of the glycerol backbone. In order to elucidate whether these acyl groups are directly chanelled into the triacylglycerols via the stepwise acylation of glycerol-3-phosphate, seed oil formation has been investigated in developing embryos of both plant species. [1-14C]Acetate labelling experiments using embryos at different stages of development, as well as the determination of the properties of the microsomal acyl-CoA:sn-glycerol-3-phosphate acyltransferase (EC 2.3.1.15) and acyl-CoA:sn-1-acylglycerol-3-phosphate acyltransferase (EC 2.3.1.51), revealed differences between the two plant species, especially with respect to the incorporation of very longchain acyl groups into the C2 position of the triacylglycerols. In microsomal fractions of developing embryos of L. douglasii both a glycerol-3-phosphate and a 1-acylglycerol-3-phosphate acyltransferase were detected which utilize very long-chain acyl-CoA thioesters as substrates. Thus, in seeds of L. douglasii very long-chain acyl groups can enter not only the C1, but also the C2 position of the triacylglycerols in the course of de-novo biosynthesis. A comparison of the properties of the acyltransferases of developing embryos with those of the corresponding activities of leaves indicates an embryo specific expression of an erucoyl-CoA-dependent microsomal 1-acylglycerol-3-phosphate acyltransferase in L. douglasii. The microsomal glycerol-3-phosphate acyltransferase of developing embryos of T. majus displayed properties very similar to those of the corresponding activity of L. douglasii. On the other hand, the microsomal 1-acylglycerol-3-phosphate acyltransferases of the two plant species showed strikingly different substrate specificities. Irrespective of the acyl groups of 1-acylglycerol-3-phosphate and regardless of whether acyl-CoA thioesters were offered separately or in mixtures, the enzyme of T. majus, in contrast to that of L. douglasii, was inactive with erucoyl-CoA. These results of the enzyme studies correspond well with those of the [1-14C]acetate labelling experiments and thus indicate that T. majus has developed mechanisms different from those of L. douglasii for the incorporation of erucic acid into the C2 position of its triacylglycerols.
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Abbreviations
- GPAT:
-
acyl-CoA:sn-glycerol-3-phosphate acyltransferase (EC 2.3.1.15)
- LPAT:
-
acyl-CoA:sn-1-acylglycerol-3-phosphate acyltransferase (EC 2.3.1.51)
References
Andrews, J., Heinz, E. (1987) Desaturation of newly synthesized monogalactosyldiacylglycerol in spinach chloroplasts. J. Plant Physiol. 131, 76–90
Bafor, M., Stobart, A.K., Stymne, S. (1990) Properties of the glycerol acylation enzymes in microsomal preparations from the developing seeds of safflower (Carthamus tinctorius) and turnip rape (Brassica campestris) and their ability to assemble cocoabutter type fats. J. Am. Oil Chem. Soc. 67, 217–225
Bernerth, R., Frentzen, M. (1990) Utilization of erucoyl-CoA by acyltransferases from developing seeds of Brassica napus L. involved in triacylglycerol biosynthesis. Plant Science 67, 21–28
Bertrams, M., Heinz, E. (1981) Positional specificity and fatty acid selectivity of purified sn-glycerol 3-phosphate acyltransferase from chloroplasts. Plant Physiol. 68, 653–657
Bradford, M.M. (1976) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal. Biochem. 72, 248–254
Brockerhoff, H. (1965) A stereospecific analysis of triglycerides. J. Lipid Res. 6, 10–15
Browse, J., Somerville, C. (1991) Glycerolipid synthesis: biochemistry and regulation. Annu. Rev. Plant Physiol. Plant Mol. Biol. 42, 467–506
Cao, Y., Oo, K.-C., Huang, A.H.C. (1990) Lysophosphatidate acyltransferase in the microsomes from maturing seeds of meadowfoam (Limnanthes alba). Plant Physiol. 94, 1199–1206
Fehling, E., Murphy, D.J., Mukherjee, K.D. (1990) Biosynthesis of triacylglycerols containing very long chain monounsaturated acyl moieties in developing seeds. Plant Physiol. 94, 492–498
Frentzen, M., Heinz, E., McKeon, T.A., Stumpf, P.K. (1983) Specificities and selectivities of glycerol-3-phosphate acyltransferase and monoacylglydrol-3-phosphate acyltransferase from pea and spinach chloroplasts. Eur. J. Biochem. 129, 629–636
Hares, W., Frentzen, M. (1987) Properties of the microsomal acylCoA: sn-1-acyl-glycerol-3-phosphate acyltransferase from spinach (Spinacia oleracea L.) leaves. J. Plant Physiol. 131, 49–59
Hares, W., Frentzen, M. (1991) Substrate specificities of the membrane-bound and partially purified microsomal acyl-CoA: 1-acyl-glycerol-3-phosphate acyltransferase from etiolated shoots of Pisum sativum (L.). Planta 185, 124–131
Harlow, D., Litchfield, C., Reiser, R. (1966) Erucic acid oils and fish oils. Lipids 1, 216–220
Ichihara, K. (1984) sn-Glycerol-3-phosphate acyltransferase in a particulate fraction from maturing safflower seeds. Arch. Biochem. Biophys. 232, 685–698
Ichihara, J., Asahi, T., Fuyi, S. (1987) 1-Acyl-sn-glycerol-3-phosphate acyltransferase in maturing safflower seeds and its contribution to the non-random fatty acid distribution of triacylglycerol. Eur. J. Biochem. 167, 339–347
Lardans, A., Trémolières, A. (1991) Accumulation of C20 and C22 unsaturated fatty acids in triacylglycerols from developing seeds of Limnanthes alba. Phytochemistry 30, 3955–3961
Mattson, F.H., Volpenhein, R.A. (1961) The specific distribution of fatty acids in the glycerides of vegetable fats. J. Biol. Chem. 236, 1891–1894
Miller, R.W., Daxenbichler, M.E., Earle, F.R. (1964) Search for new industrial oils. VIII. The genus Limnanthes. J. Am. Oil Chem. Soc. 41, 167–169
Oo, K.-C., Huang, A.H.C. (1989) Lysophosphatidate acyltransferase activities in the microsomes from palm endosperm, maize scutellum, and rapeseed cotyledon of maturing seeds. Plant Physiol. 91, 1288–1295
Phillips, B.E., Smith, Jr. C.R., Tallent, W.H. (1970) Glycerides of Limnanthes douglasii seed oil. Lipids 6, 93–99
Pollard, M.R., Stumpf, P.K. (1980a) Long chain (C20 and C22) fatty acid biosynthesis in developing seeds of Tropaeolum majus. An in vivo study. Plant Physiol. 66, 641–648
Pollard, M.R., Stumpf, P.K. (1980b) Biosynthesis of C20 and C22 fatty acids by developing seeds of Limnanthes alba. Chain elongation and Δ-5 desaturation. Plant Physiol. 66, 649–655
Radwan, S.S. (1976) Localization of lipids containing (z)-11-eicosenoic acid and (z)-13-docosenoic acid in Tropaeolum majus. Phytochemistry 15, 1727–1729
Siebertz, H.P., Heinz, E., Linscheid, M., Joyard, J., Douce, R. (1979) Characterization of lipids from chloroplast envelopes. Eur. J. Biochem. 101, 429–438
Smith, Jr. C.R., Bagby, M.O., Miwa, T.K., Lohmar, R.L., Wolff, J.A. (1960) Unique fatty acids from Limnanthes douglasii seed oil: The C20- and C22-monoenes. J. Org. Chem. 25, 1770–1774
Sukumar, V., Sastry, P.S. (1987) Triacylglycerol synthesis in developing seeds of groundnut (Arachis hypogaea): acyl CoA synthetase and sn-glycerol-3-phosphate acyltransferase in the maturing seed. Biochem. Intern. 14, 719–726
Sun, C., Cao, Y., Huang, A.H.C. (1988) Acyl-coenzyme A preference of the glycerol phosphate pathway in the microsomes from the maturing seeds of palm, maize, and rapeseed. Plant Physiol, 88, 56–60
Ullman, M.D., McCluer, R.H. (1977) Quantitative analysis of plasma neutral glycosphingolipids by high performance liquid chromatography of their perbenzoyl derivatives. J. Lipid Res. 18, 371–378
Wolter, F.P., Bernerth, R., Löhden, I., Schmidt, V., Peterek, G., Frentzen, M. (1991) Biochemische und molekularbiologische Ansätze zur Veränderung der Fettsäurezusammensetzung des Rapsöls. Fett Wiss. Technol. 93, 288–290
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This work was supported by the Bundesministerium für Forschung und Technologie (Förderkennzeichen 0316600A).
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Löhden, I., Frentzen, M. Triacylglycerol biosynthesis in developing seeds of Tropaeolum majus L. and Limnanthes douglasii R. Br.. Planta 188, 215–224 (1992). https://doi.org/10.1007/BF00216816
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DOI: https://doi.org/10.1007/BF00216816