Table 2.
13C serine labeling and model-optimized flux ratios with [1,2-13C] glucose
Serine 13C isotopologue content (%) | Modeled flux ratios (%) | |||||||
---|---|---|---|---|---|---|---|---|
M | M1 | M2 | M3 |
(R5) |
(R6) |
(R7) |
Model error (%) | |
T47D | 82.21±0.65 a (82.21±0.65) | 14.16±0.50 a (14.16±0.50) | 3.46±0.19 a (3.46±0.19) | 0.17±0.02 a (0.17±0.02) | 29.9±2.9 a | 13.9±10.0 a | 11.0±0.3 a | 0.01±0.01 |
MDA231 | 95.25±0.37 b (nd) | 3.88±0.29 b (nd) | 0.84±0.07 b (nd) | 0.03±0.04 b (nd) | 0 b | nd | nd | nd |
BoM | 67.93±4.73 a,c (67.93±4.73) | 20.53±2.91 a (20.50±2.89) | 11.04±1.74 c (11.04±1.74) | 0.49±0.08 c (0.53±0.11) | 69.0±14.6 a | 19.8±16.1 a | 6.6±0.3 b | 0.10±0.08 |
LM | 66.58±2.69 c (66.58±2.69) | 19.36±1.48 a (19.36±1.48) | 13.43±1.16 c (13.43±1.16) | 0.64±0.07 c (0.63±0.07) | 63.9±10.4 a | 36.6±20.1 a | 5.6±0.2 c | 0.01±0.01 |
Experiments with [1,2-13C] glucose were conducted as detailed in Table 1. 13C serine labeling (mean ± SEM, n=6) is expressed as percent contribution of each isotopologue to total extracellular serine (M, M1, M2, and M3 denote serine with none, one, two, two, or three 13C atoms, respectively). Data in parentheses are simulated serine labeling (mean ± SEM, n=6) from Model 2-optimized flux ratios R5, R6, and R7. Model error was calculated as the sum of the absolute values of the difference between the measured and calculated M-M3 serine. Within a column, means sharing common superscripts do not significantly differ. Background 13C abundance in serine standards averaged 95.17±0.38, 4.06±0.33, 0.76±0.05, and 0.01±0.00 % for M, M1, M2, and M3 isotopologues, respectively. Note that the table reports total serine labeling not corrected for background. Nd: not determined