Table 1.

Kinetics of osmotic-gradient- and cold-activated glycine betaine transporta

ConditionsbKm (μM GB)Vmax (pmol of GB/min · mg of protein)
30°C + 600 mOsm sucrose2.9 ± 0.13,730 ± 60
30°C + 600 mOsm KCl1.2 ± 0.12,200 ± 200
4°C, no additions15.7 ± 0.328 ± 2.4
  • a Abbreviations: GB, glycine betaine;V max, maximum rate of transport. Reported errors are standard errors of at least two experiments, each run in duplicate. Data were analyzed using the program Enzyme Kinetics, version 1.1 (Trinity software); values were calculated using fourth-power weighting.

  • b All assay mixtures contained 50 mM potassium phosphate (pH 7.0), 10 mM MgSO4, 20 mM potassium ascorbate, and 200 μM PMS.