TABLE 1.
Comparison of the steady-state glucose consumption rate with the zero trans-influx kinetics of glucose transport and the intracellular glucose concentration in derepressed and repressed cellsa
| Extracellular glucose concn (mM) | Vmax (nmol · min−1 · mg of protein−1) | Km (mM) | Calculated zero transinflux rate (nmol · min−1 · mg of protein−1) | Measured intracellular glucose concn (mM) | Measured glucose consumption rate (nmol · min−1 · mg of protein−1) | Calculated glucose consumption rate (nmol · min−1 · mg of protein−1) |
|---|---|---|---|---|---|---|
| Derepressed cells | ||||||
| 13.3 | 536 ± 12 | 1.7 ± 0.1 | 475 ± 10 | 1.5 ± 0.1 | 220 ± 16 | 233 |
| 34 | 536 ± 12 | 1.7 ± 0.1 | 511 ± 11 | 1.6 ± 0.1 | 245 ± 18 | 261 |
| Repressed cells | ||||||
| 9.4 | 614 ± 38 | 55 ± 5 | 90 ± 8 | <0.1 | 145 ± 16 | 88 |
| 36 | 614 ± 38 | 55 ± 5 | 243 ± 15 | <0.1 | 420 ± 38 | 240 |
| 255 | 614 ± 38 | 55 ± 5 | 503 ± 31 | 2.7 ± 0.5 | 568 ± 55 | 481 |
a
Values are means ± standard deviations. Values for Vmax and Km were measured as described in Walsh et al. (45). Estimation of the glucose consumption rate was based on the assumption that the facilitated diffusion carrier is symmetrical, and estimates were obtained by using the rate equation detailed in Appendix.