Estimated Drainage of Carbon from the Tricarboxylic Acid Cycle for Protein Synthesis in Suspension Cultures of Paul's Scarlet Rose Cells

The amount of carbon (mumoles of carbon atoms) drained from the tricarboxylic acid cycle for protein synthesis was compared with mumoles of CO(2) released from the cycle at 2-day intervals during the growth of suspension cultures of Paul's Scarlet rose. We concluded that during the period of most rapid protein synthesis (day 0-4) one-sixth as much carbon was drained from the tricarboxylic acid cycle for protein synthesis as was released as CO(2). By day 8, one-thirtieth of the amount of carbon released as CO(2) was incorporated into protein. Net protein synthesis stopped on day 8, but the evolution of CO(2)/culture continued at its maximum rate until day 10.Similar ratios were calculated based on the recovery of (14)C in protein versus CO(2) following a 3-hr provision of labeled substrates to 3-day-old cells (age of maximum protein synthesis). Provision of acetate-1-(14)C and acetate-2-(14)C indicated from one-eighth to an equal amount of carbon was incorporated into protein as was released as CO(2). When (14)C-labeled intermediates of the tricarboxylic acid cycle were provided, the ratio of (14)C incorporated into protein versus that evolved in CO(2) ranged from 1/0.9 to 1/4.9.Following a critical analysis of the methods used, it was concluded that during periods of rapid protein synthesis, a conservative estimate of the amount of carbon drained from the tricarboxylic acid cycle for protein synthesis was one-fourth of the amount evolved as CO(2) from the cycle.