Table I.
Sensitivity of the sorbitol transporter (PcSOT1 and PcSOT2) activity to inhibitor (at the indicated concentration) and other sugar or sugar alcohol substances (5 mm)
| Added Compound | Relative Uptake Rate
|
|
|---|---|---|
| PcSOT1 | PcSOT2 | |
| % | ||
| None | 100 | 100 |
| 50 μm CCCP | 3.2 | 7.6 |
| 100 μm PCMBS | 93.4 | 83.7 |
| Man | 19.1 | 53.7 |
| Suc | 78.3 | 93.7 |
| Glc | 6.1 | 26.1 |
| Fru | 16.1 | 35.5 |
| Xylitol | 75.7 | 96.1 |
| Mannitol | 21.3 | 48.5 |
The substances were added 30 s prior to 14C- or 3H-labeled sorbitol. All uptake tests were performed at 0.5 mm sorbitol (pH 4.5), and incubation time was 3 min. Control activities (100%) were 5.19 and 4.03 nmol mg−1 protein min−1 for PcSOT1 and PcSOT2, respectively. The results are the means of four replicates expressed as relative uptake rate to sorbitol.