De novo CDP‐choline‐dependent glycerophosphorylcholine synthesis and its involvement as an intermediate in phosphatidylcholine synthesis

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Abstract
The activity of CDP‐choline‐dependent glycerophosphorylcholine synthetase (CDP‐choline:sn‐3‐glycerophosphate cholinetransferase), a newly discovered enzyme involved in the recently proposed pathways of acyl‐specific phosphatidylcholine synthesis, is reported in rat liver. Endogenous CDP‐choline, synthesized via the CMP‐driven back reaction of phosphorylcholine transferase, is also shown to be a choline donor for this glycerophosphorylcholine synthetase. The function of glycerophosphorylcholine as an intermediate in phosphatidylcholine synthesis is demonstrated by specific isotope trapping whereby unlabelled glycerophosphorylcholine inhibited label incorporation from sn‐[14C]glycerol‐3‐phosphate into phosphatidylcholine in mouse gastrocnemius, a tissue that is essentially devoid of the cytidine pathway for phosphatidylcholine synthesis and uses a non‐allelic glycerophosphorylcholine synthetase (exogenous PC:sn‐3‐glycerophosphate cholinetransferase) in the synthesis of glycerophosphorylcholine.