Biosynthesis of phosphatidylcholine in young seedlings of Raphanus sativus is supplied with choline from degradation of the seed constituent sinapine (sinapoylcholine). This conclusion has been deduced from the following results:
(1) Raphanus sativus seedlings accumulate approx. 70 nmol phosphatidylcholine which may be relevant for the consumption of choline, liberated during hydrolysis of approx. 130 nmol sinapine.
(2) [14C]choline and [14C]ethanolamine, taken up by germinating Raphanus seeds, are exclusively consumed in the biosynthesis of phosphatidylcholine and phosphatidylethanolamine, respectively.
(3) Pulse-chase experiments with seedlings at different germination stages show a reduced [14C]choline incorporation into phosphatidylcholine at the time when degradation of sinapine occurs, obviously as a result of an isotope dilution by an increase of the endogenous choline pool.
(4) After [14C]choline pulse to immature seeds, during the process of seed maturation most of the activity taken up is incorporated into accumulating sinapine and approx. 50% compared to this into phosphatidylcholine. During seedling development the quantity of labelled sinapine rapidly decreases as a result of sinapine degradation with a concomitant label increase in free choline, phosphorylcholine, and phosphatidylcholine. Approx. 50% of the choline liberated from sinapine, is consumed in the biosynthesis of phosphatidylcholine.
High performance liquid chromatographic analyses of phosphatidylcholine during Raphanus germination revealed that this phospholipid might be a metabolically active compound. Changes in the absorptivity of this compound at 210 nm indicate changes in the degree of unsaturation in the fatty acyl groups
A Journal of Biosciences: Zeitschrift für Naturforschung C (ZNC) is an international scientific journal for the emerging field of natural and natural-like products. ZNC publishes original research on the isolation, bio-chemical synthesis and bioactivities of natural products, their biochemistry, pharmacology, biotechnology, and biological activity and innovative developed computational methods for predicting their structure and/or function.