Abstract
1. The addition of mitochondria to an incubation system containing the soluble and microsomal fractions of rat liver enhances severalfold the incorporation of each of ethanolamine, phosphorylethanolamine and CDP-ethanolamine into phosphatidylethanolamine. 2. In the presence of microsomal, mitochondrial and soluble fractions, CDP-ethanolamine exhibits the greatest initial rate of incorporation (approx. 6nmol/h per mg of protein), being slightly faster than that of phosphorylethanolamine (approx. 5nmol/h per mg of protein). Incorporation of ethanolamine proceeds very slowly for the first 20min and only after 30min gives rates approaching those of the other two precursors. 3. By using a substrate `dilution' technique it was shown that in the reconstituted system the affinity of each of the enzymes for their respective substrates is very high: 10μm for ethanolamine, 25μm for phosphorylethanolamine and 5μm for CDP-ethanolamine. 4. Isolation of the mitochondrial and microsomal fractions from the medium after incubation together with phosphorylethanolamine showed that about 70% of the total radioactivity was present in the microsomal fraction and about 30% in the mitochondria after only 20min. Similar experiments with ethanolamine as precursor revealed that after 20min only about 15% of the total radioactivity was present in the mitochondria but that after 40min about 30% was present in this fraction. 5. Heating and phospholipase treatment of mitochondria, but not freeze-thawing, eliminated the stimulatory effect of mitochondria on phospholipid synthesis. 6. The reconstituted system exhibits an absolute requirement for Mg2+ (2mm gave maximal rates) and is inhibited by very low concentrations of Ca2+ (100μm-Ca2+ produced half-maximal inhibition with 3mm-Mg2+). Further addition of Mg2+ overcame the Ca2+ inhibition, suggesting that the inhibitory effect is readily reversible. 7. The concept that modification of the Mg2+/Ca2+ ratio is a means of controlling the rate of cellular phospholipid synthesis is introduced.
Full text
PDF








Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Allen R. J. The estimation of phosphorus. Biochem J. 1940 Jun;34(6):858–865. doi: 10.1042/bj0340858. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bygrave F. L. Studies on the interaction of metal ions with pyruvate kinase from Ehrlich ascites-tumour cells and from rabbit muscle. Biochem J. 1966 Nov;101(2):488–494. doi: 10.1042/bj1010488. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bygrave F. L. The effect of calcium ions on the glycolytic activity of Ehrlich ascites-tumour cells. Biochem J. 1966 Nov;101(2):480–487. doi: 10.1042/bj1010480. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bygrave F. L. The ionic environment and metabolic control. Nature. 1967 May 13;214(5089):667–671. doi: 10.1038/214667a0. [DOI] [PubMed] [Google Scholar]
- DAWSON R. M. A hydrolytic procedure for the identification and estimation of individual phospholipids in biological samples. Biochem J. 1960 Apr;75:45–53. doi: 10.1042/bj0750045. [DOI] [PMC free article] [PubMed] [Google Scholar]
- KENNEDY E. P. Biosynthesis of complex lipids. Fed Proc. 1961 Dec;20:934–940. [PubMed] [Google Scholar]
- KENNEDY E. P. The synthesis of cytidine diphosphate choline, cytidine diphosphate ethanolamine, and related compounds. J Biol Chem. 1956 Sep;222(1):185–191. [PubMed] [Google Scholar]
- KENNEDY E. P., WEISS S. B. The function of cytidine coenzymes in the biosynthesis of phospholipides. J Biol Chem. 1956 Sep;222(1):193–214. [PubMed] [Google Scholar]
- Lehninger A. L., Carafoli E., Rossi C. S. Energy-linked ion movements in mitochondrial systems. Adv Enzymol Relat Areas Mol Biol. 1967;29:259–320. doi: 10.1002/9780470122747.ch6. [DOI] [PubMed] [Google Scholar]
- 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]
- McMurray W. C., Magee W. L. Phospholipid metabolism. Annu Rev Biochem. 1972;41(10):129–160. doi: 10.1146/annurev.bi.41.070172.001021. [DOI] [PubMed] [Google Scholar]
- Meli J., Bygrave F. L. The role of mitochondria in modifying calcium-sensitive cytoplasmic metabolic activities. Modification of pyruvate kinase activity. Biochem J. 1972 Jun;128(2):415–420. doi: 10.1042/bj1280415. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Porcellate G., Biasion M. G., Pirotta M. The labeling of brain ethanolamine phosphoglycerides from cytidine diphosphate ethanolamine in vitro. Lipids. 1970 Sep;5(9):734–742. doi: 10.1007/BF02531385. [DOI] [PubMed] [Google Scholar]
- Porcellati G., Biasion M. G., Arienti G. The incorporation of phosphorylethanolamine into the phospholipids of brain microsomes in vitro. Lipids. 1970 Sep;5(9):725–733. doi: 10.1007/BF02531384. [DOI] [PubMed] [Google Scholar]
- SCHNEIDER W. C. INTRACELLULAR DISTRIBUTION OF ENZYMES. XIII. ENZYMATIC SYNTHESIS OF DEOXYCYTIDINE DIPHOSPHATE CHOLINE AND LECITHIN IN RAT LIVER. J Biol Chem. 1963 Nov;238:3572–3578. [PubMed] [Google Scholar]
- SWANSON M. A. Phosphatases of liver. I. Glucose-6-phosphatase. J Biol Chem. 1950 Jun;184(2):647–659. [PubMed] [Google Scholar]
- Shephard E. H., Hübscher G. Phosphatidate biosynthesis in mitochondrial subfractions of rat liver. Biochem J. 1969 Jun;113(2):429–440. doi: 10.1042/bj1130429. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Spencer T., Bygrave F. L. Modification by calcium ions of adenine nucleotide translocation in rat liver mitochondria. Biochem J. 1972 Sep;129(2):355–365. doi: 10.1042/bj1290355. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Spencer T., Bygrave F. L. The role of mitochondria in modifying the cellular ionic environment: studies of the kinetic accumulation of calcium by rat liver mitochondria. J Bioenerg. 1973 Apr;4(3):347–362. doi: 10.1007/BF01648977. [DOI] [PubMed] [Google Scholar]
- THIERS R. E., VALLEE B. L. Distribution of metals in subcellular fractions of rat liver. J Biol Chem. 1957 Jun;226(2):911–920. [PubMed] [Google Scholar]
- WILGRAM G. F., KENNEDY E. P. INTRACELLULAR DISTRIBUTION OF SOME ENZYMES CATALYZING REACTIONS IN THE BIOSYNTHESIS OF COMPLEX LIPIDS. J Biol Chem. 1963 Aug;238:2615–2619. [PubMed] [Google Scholar]
- Weinhold P. A., Rethy V. B. Ethanolamine phosphokinase: activity and properties during liver development. Biochim Biophys Acta. 1972 Jul 13;276(1):143–154. doi: 10.1016/0005-2744(72)90015-0. [DOI] [PubMed] [Google Scholar]
- Williams M. L., Bygrave F. L. Incorporation of inorganic phosphate into phospholipids by the homogenate and by sub-cellular fractions of rat liver. Eur J Biochem. 1970 Nov;17(1):32–38. doi: 10.1111/j.1432-1033.1970.tb01129.x. [DOI] [PubMed] [Google Scholar]
