Table 2. Dissociation constants of selected Pns to the E. coli PhnD and to two different PhnD versions of Prochlorococcus MIT9301 measured at 30 °C.
|
Ligand |
PhnD1 |
PhnD2 |
E. coli |
|
|---|---|---|---|---|
| Name | Abbreviation | Kd (μ) | ||
| Phosphate | Pi | 54.9a | − | − |
| Phosphite | 0.12 | 2.0 | − | |
| Methylphosphonate | MPn | 39.0 | 0.8 | 18.4 |
| Ethylphosphonate | EPn | − | 2.8 | 1.4 |
| Aminomethylphosphonate | AMPn | − | − | 16.6 |
| 2-aminoethylphosphonate | 2-AEPn | − | − | 0.1 |
| Phosphonoacetate | PnAc | − | − | 17.8 |
a
The high Kd value observed for Pi with Prochlorococcus PhnD1 are 30 times higher than the highest deep sea P concentrations and are therefore environmentally irrelevant. ‘−' Denotes no binding detected.