Phospholipid Synthesis in Aging Potato Tuber Tissue

Abstract

Abstract. The effect of activation ("aging") of potato tuber slices on their phospholipid metabolism was investigated. Aged slices were incubated with 14C labeled choline, ethanolamine, methionine, serine, and acetate. In all cases, the incorporation of radioactivity into the lipid fraction increased with the length of time the slices were aged. This inclorporation was shown to be true synthesis and not exchange between precursors and existing phospholipids.The increased incorporation of labeled choline into lipids was mainly due to an increase in its uptake by the tissue, the presence of aotidione during aging prevented this increased uptake. The increase in the incorporation of labeled acetate into lipids resullted from the development of a fatty acid synthetase during aging. In the case of ethanolamine, both its uptake into the tissue and its incorporation into the lipid fraction increased.The phospholipids formed from these precursors were identified by paper and thin-layer chromatography. The major compound formed from choline was lecithin, while phosphatidylethanolamine and a small amount of lecithin were formed from ethanolamine.

Membrane Transformations in Aging Potato Tuber Slices

“…We have previously shown that "C-choline is used to form lecithin in this system (22). The radioactive lipids in the membrane pellets do not exchange with unlabeled lecithin micelles and can be stabilized simply by boiling.…”

“…The total radioactivity before fractionation was determined on identical tissue samples incubated in the same way. These samples were extracted directly with chloroform-methanol (22) for the determination of lipoidal radioactivity and with dilute trichloroacetic acid for the determination of proteinaceous radioactivity. The total lipoidal radioactivity derived from acetate-1-14C was 250,000 cpm, and that from choline-1,2-14C, 75,000 cpm; the proteinaceous radioactivity was 265,000 cpm.…”

“…The total radioactivity before fractionation was determined on an equal number of slices contained in another flask and incubated in the same way. At the end of the incubation these slices were rinsed, blotted, and extracted directly with chloroform-methanol (22). On this basis, we estimate the total recovery of lipoidal radioactivity to be 79% for the 2-hr-old slices and 88% for the 9-hr-old slices.…”

“…The source of materials and the basic procedures for preparation of potato tuber slices, aging, the incorporation of radioactive lipid precursors into slices, and the assay of lipid-soluble radioactivity have been described previously (22).…”

“…pholipids of aging potato tuber slices was investigated by Tang and Castelfranco (22), Ben Abdelkader (4), and Ben Abdelkader and Mazliak (5).…”