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Choline biosynthesis by a preparation enriched in synaptosomes from rat brain
Nature
|April 2, 1981
Summary
Brain cells can synthesize choline de novo using phosphatidylethanolamine N-methyltransferase (PeMT). This enzyme metabolizes phosphatidylcholine (PC) to release free choline, challenging previous assumptions about brain choline sources.
Area of Science:
- Neuroscience
- Biochemistry
Background:
- The prevailing view is that brain cells cannot synthesize choline de novo, relying solely on circulation uptake for acetylcholine and membrane synthesis.
- This view conflicts with observed net choline efflux from the brain.
Purpose of the Study:
- To investigate the capacity of mammalian brain preparations to synthesize and release free choline.
- To explore the role of phosphatidylethanolamine N-methyltransferase (PeMT) in brain choline metabolism.
Main Methods:
- Enzyme assays on mammalian brain preparations, specifically synaptosomal fractions.
- Analysis of phosphatidylcholine (PC) metabolism using S-adenosylmethionine (SAM) as a methyl donor.
Main Results:
- Mammalian brain preparations contain phosphatidylethanolamine N-methyltransferase (PeMT) activity, catalyzing the synthesis of phosphatidylcholine (PC) from phosphatidylethanolamine (PE) using SAM.
- Rat brain synaptosomal preparations demonstrated the ability to metabolize PC synthesized by PeMT, liberating free choline.
Conclusions:
- Mammalian brain cells possess the enzymatic machinery (PeMT) for de novo synthesis of PC.
- Brain synaptosomes can further metabolize this newly synthesized PC to release free choline, suggesting an endogenous source for brain choline.