Contribution of Nonautotrophic Carbon Dioxide Fixation to Protein Synthesis in Suspension Cultures of Paul's Scarlet Rose

Abstract

Bicarbonate-(14)C was provided to 5- and 11-day-old suspension cultures of Paul's Scarlet rose, and the incorporation of (14)C into lipid, protein, amino acids, and organic acids was determined. The rate of bicarbonate uptake was approximately the same by 5- and 11-day-old cells, but the distribution of (14)C among cell constituents was markedly different. In 5-day-old cells a larger proportion of the (14)C entered protein, whereas in 11-day-old cells there was a greater tendency for (14)C to accumulate in malate.The (14)C in protein was distributed among 10 amino acids each having greater than 1% of the total (14)C recovered in protein. The distribution of (14)C among tricarboxylic acid cycle intermediates indicated that the aspartate family of amino acids was synthesized directly from oxaloacetate produced as a result of nonautotrophic CO(2) fixation. However, this was not the sole source of oxaloacetate used for the synthesis of aspartate, for in a double labeling study with bicarbonate-(14)C and acetate-(3)H it was shown that oxaloacetate was drained simultaneously from the tricarboxylic acid cycle for this purpose.