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. 1976 Feb;57(2):218–223. doi: 10.1104/pp.57.2.218

Phospholipid Synthesis and Exchange in Castor Bean Endosperm Homogenates 1

J Michael Lord a
PMCID: PMC541995  PMID: 16659454

Abstract

Crude organelle preparations from castor bean (Ricinus communis L.) endosperm rapidly incorporate CDP-(14C)choline and CDP-(14C)-ethanolamine into phosphatidylcholine and phosphatidylethanolamine, respectively. Separation of organelles by sucrose density gradient centrifugation following incubation with these substrates demonstrated that most of the 14C phospholipids thus formed were present in the endoplasmic reticulum membranes, although label was also found in mitochondria, proplastids, and glyoxysomes. The phospholipid-synthesizing enzymes, cholinephosphotransferase and ethanolaminephosphotransferase, are exclusively confined to the endoplasmic reticulum membrane fraction, suggesting that the appearance of 14C-phospholipid in other organelles was due to phospholipid exchange. Phospholipid synthesis was inhibited by the cytoplasmic supernatant fraction. The active inhibitor in this fraction was not identified, but the inhibition was not significantly relieved by either dialyzing or boiling the supernatant. Phosphatidylcholine synthesis showed an absolute requirement for Mg2+; the Michaelis constant was 1 mm. Ca2+ was a potent inhibitor of Mg2+-stimulated phospholipid synthesis and enhanced the decay of 14C-phospholipids from pre-labeled membranes, particularly when the membranes were resuspended in the cytoplasmic supernatant.

The data are consistent with the concept that the endoplasmic reticulum is a major site of membrane proliferation where structural lipids, and possibly proteins, are inserted into, and thus expand, a pre-existing membrane fraction. Other organelle and cellular membranes could therefore originate from the proliferating endoplasmic reticulum by a process of membrane flow and differentiation.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Abdelkader A. B., Mazliak P. Echanges de lipides entre mitochondries, microsomes et surnageant cytoplasmique de cellules de pomme de terre ou de chou-fleur. Eur J Biochem. 1970 Aug;15(2):250–262. doi: 10.1111/j.1432-1033.1970.tb01002.x. [DOI] [PubMed] [Google Scholar]
  2. Beevers H. Glyoxysomes of castor bean endosperm and their relation to gluconeogenesis. Ann N Y Acad Sci. 1969 Dec 19;168(2):313–324. doi: 10.1111/j.1749-6632.1969.tb43118.x. [DOI] [PubMed] [Google Scholar]
  3. Bowden L., Lord J. M. Development of phospholipid synthesizing enzymes in castor bean endosperm. FEBS Lett. 1975 Jan 1;49(3):369–371. doi: 10.1016/0014-5793(75)80787-3. [DOI] [PubMed] [Google Scholar]
  4. Bracker C. E., Grove S. N. Continuity between cytoplasmic endomembranes and outer mitochondrial membranes in fungi. Protoplasma. 1971;73(1):15–34. doi: 10.1007/BF01286408. [DOI] [PubMed] [Google Scholar]
  5. CARO L. G., PALADE G. E. PROTEIN SYNTHESIS, STORAGE, AND DISCHARGE IN THE PANCREATIC EXOCRINE CELL. AN AUTORADIOGRAPHIC STUDY. J Cell Biol. 1964 Mar;20:473–495. doi: 10.1083/jcb.20.3.473. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Cooper T. G., Beevers H. Mitochondria and glyoxysomes from castor bean endosperm. Enzyme constitutents and catalytic capacity. J Biol Chem. 1969 Jul 10;244(13):3507–3513. [PubMed] [Google Scholar]
  7. Franke W. W., Kartenbeck J. Outer mitochondrial membrane continuous with endoplasmic reticulum. Protoplasma. 1971;73(1):35–41. doi: 10.1007/BF01286409. [DOI] [PubMed] [Google Scholar]
  8. Hruban Z., Rechcigl M., Jr Microbodies and related particles. Morphology, biochemistry, and physiology. Int Rev Cytol. 1969;(Suppl):1–296. [PubMed] [Google Scholar]
  9. Johnson K. D., Kende H. Hormonal Control of Lecithin Synthesis in Barley Aleurone Cells: Regulation of the CDP-Choline Pathway by Gibberellin. Proc Natl Acad Sci U S A. 1971 Nov;68(11):2674–2677. doi: 10.1073/pnas.68.11.2674. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Kader J. C. Proteins and the intracellular exchange of lipids. I. Stimulation of phospholipid exchange between mitochondria and microsomal fractions by proteins isolated from potato tuber. Biochim Biophys Acta. 1975 Jan 24;380(1):31–44. [PubMed] [Google Scholar]
  11. Kagawa T., Lord J. M., Beevers H. The origin and turnover of organelle membranes in castor bean endosperm. Plant Physiol. 1973 Jan;51(1):61–65. doi: 10.1104/pp.51.1.61. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Kamath S. A., Rubin E. The exchange of phospholipids between subcellular organelles of the liver. Arch Biochem Biophys. 1973 Sep;158(1):312–322. doi: 10.1016/0003-9861(73)90627-9. [DOI] [PubMed] [Google Scholar]
  13. Lord J. M., Kagawa T., Beevers H. Intracellular distribution of enzymes of the cytidine diphosphate choline pathway in castor bean endosperm. Proc Natl Acad Sci U S A. 1972 Sep;69(9):2429–2432. doi: 10.1073/pnas.69.9.2429. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Lord J. M., Kagawa T., Moore T. S., Beevers H. Endoplasmic reticulum as the site of lecithin formation in castor bean endosperm. J Cell Biol. 1973 Jun;57(3):659–667. doi: 10.1083/jcb.57.3.659. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. McMurray W. C., Dawson R. M. Phospholipid exchange reactions within the liver cell. Biochem J. 1969 Mar;112(1):91–108. doi: 10.1042/bj1120091. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Moore T. S., Lord J. M., Kagawa T., Beevers H. Enzymes of phospholipid metabolism in the endoplasmic reticulum of castor bean endosperm. Plant Physiol. 1973 Jul;52(1):50–53. doi: 10.1104/pp.52.1.50. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Morré D. J., Nyquist S., Rivera E. Lecithin Biosynthetic Enzymes of Onion Stem and the Distribution of Phosphorylcholine-Cytidyl Transferase among Cell Fractions. Plant Physiol. 1970 Jun;45(6):800–804. doi: 10.1104/pp.45.6.800. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Redman C. M., Siekevitz P., Palade G. E. Synthesis and transfer of amylase in pigeon pancreatic micromosomes. J Biol Chem. 1966 Mar 10;241(5):1150–1158. [PubMed] [Google Scholar]
  19. Vigil E. L. Cytochemical and developmental changes in microbodies (glyoxysomes) and related organelles of castor bean endosperm. J Cell Biol. 1970 Sep;46(3):435–454. doi: 10.1083/jcb.46.3.435. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. WEISS S. B., SMITH S. W., KENNEDY E. P. The enzymatic formation of lecithin from cytidine diphosphate choline and D-1,2-diglyceride. J Biol Chem. 1958 Mar;231(1):53–64. [PubMed] [Google Scholar]
  21. Wirtz K. W.A., Zilversmit D. B. Partial purification of phospholipid exchange protein from beef heart. FEBS Lett. 1970 Mar 16;7(1):44–46. doi: 10.1016/0014-5793(70)80614-7. [DOI] [PubMed] [Google Scholar]
  22. Wirtz K. W., Kamp H. H., van Deenen L. L. Isolation of a protein from beef liver which specifically stimulates the exchange of phosphatidylcholine. Biochim Biophys Acta. 1972 Aug 9;274(2):606–617. doi: 10.1016/0005-2736(72)90207-6. [DOI] [PubMed] [Google Scholar]

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