Acetate Metabolism in Cell Suspension Cultures

Abstract

Cell suspension cultures of Paul's Scarlet rose were grown over a 14-day period, during which a 50-fold increase in fresh weight occurred. Three phases could be recognized from weight, DNA determinations, and microscopic examination. From days 0 to 7, cell division was accompanied by cell expansion; from days 7 to 10, only cell expansion occurred; and from days 10 to 14, there was no further growth.When acetate-1-(14)C was supplied continuously to 4-day and 12-day cells, (14)C was readily incorporated into lipid, CO(2), organic acids, amino acids, and protein. In the older cells, relatively greater amounts of (14)C were recovered in organic and amino acids, and accumulation of (14)C in these components continued after a steady rate of incorporation of (14)C into protein and (14)CO(2) had been established.Glutamate-(14)C was the most heavily labeled compound recovered after a pulse of acetate-1-(14)C in both cell types and was depleted when acetate-1-(14)C was removed, particularly rapidly in 4-day cells. (14)C was rapidly lost from the malate-(14)C labeled during the pulse of acetate-1-(14)C in 4-day cells, whereas malate-(14)C continued to increase in 12-day cells after the pulse. Glutamate-(14)C was shown to be the source of the (14)C accumulating in malate in 12-day cells.Several other soluble amino acids were labeled during a pulse of acetate-(14)C in both cell types. After the pulse most of the (14)C lost from these was recovered in the corresponding amino acid in protein, showing that only protein precursor pools had been labeled. The behavior of asparagine was exceptional since its (14)C content increased after the pulse and no turnover was apparent. The kinetics of labeling of aspartate, malate, and CO(2) showed that oxaloacetate generated in the tricarboxylic acid cycle following the pulse was not in equilibrium with aspartate.