Pathways of Membrane Phospholipid Synthesis in the Myxomycete Physarum polycephalum

P. R. Makarov,^1,2 N. A. Polteva,¹ and I. S. Yurkov¹

¹Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142292 Russia; fax: (7-095) 935-59-84.

²To whom correspondence should be addressed.

Submitted October 21, 1996; revision submitted December 2, 1996.

In the present study we investigated the synthesis of membrane phospholipids in the myxomycete Physarum polycephalum during the logarithmic growth phase using [³²P]orthophosphoric acid and [¹⁴C]ethanolamine. The label incorporation into phospholipids was shown to increase in the following order: phosphatidylcholine (PC) < phosphatidylserine (PS) < phosphatidylethanolamine (PE) < phosphatidylinositol (PI) < phosphatidic acid. For PE and PI, the rates of synthesis were 2-fold higher that those required for cell duplication. It has been established that PS is not synthesized from PE or PC and is not the main precursor of PE or PC. Only a minor part of PC is synthesized through methylation of PE; its major part is synthesized by coupling of two precursors to diacylglycerol; one of these precursors is phosphorylated inside the cell, the other is absorbed from the environment in phosphorylated form.

KEY WORDS: phospholipid synthesis, P. polycephalum.

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