Abstract
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.