Table 1.
Kinetic parameters for the hydrolysis of substrates by TNAP-, NPP1-, or TNAP + NPP1-proteoliposomes. Kinetic analysis was performed in 50 mM Tris-HCl buffer, pH 8, containing 2 mM MgCl2 and substrate.
| Substrates | Kinetic parameters |
Proteoliposomes | ||
|---|---|---|---|---|
| TNAP | NPP1 | TNAP + NPP1 | ||
| ATP | Vm (U/mg) | 446 ± 37 | 120 ± 15 | 363 ± 24 |
| K0.5 (mM) | 0.19 ± 0.01 | 0.095 ± 0.01 | 0.28 ± 0.02 | |
| n | 0.90 ± 0.07 | 0.45 ± 0.03 | 0.87 ± 0.05 | |
| kcat/K0.5 (M−1.s−1) | 4,522 | 2,741 | - | |
| PPi | Vm (U/mg) | 1,053 ± 83 | 765 ± 41 | 1,113 ± 98 |
| K0.5 (mM) | 0.19 ± 0.01 | 0.20 ± 0.008 | 0.19 ± 0.007 | |
| n | 1.5 ± 0.08 | 5.2 ± 0.4 | 4.7 ± 0.3 | |
| kcat/K0.5 (M−1.s−1) | 11,084 | 8,300 | - | |
| ADP | Vm (U/mg) | 558 ± 42 | 35 ± 2.8 | 279 ± 20 |
| K0.5 (mM) | 0.20 ± 0.02 | 0.053 ± 0.004 | 0.13 ± 0.01 | |
| n | 2.8 ± 0.1 | 1.6 ± 0.09 | 2.9 ± 0.2 | |
| kcat/K0.5 (M−1.s−1) | 5,580 | 1,433 | - | |
| AMP | Vm (U/mg) | 1,051 ± 73 | 19 ± 1.7 | 680 ± 43 |
| K0.5 (mM) | 1.1 ± 0.08 | 0.71 ± 0.05 | 0.76 ± 0.03 | |
| n | 2.0 ± 0.1 | 4.2 ± 0.2 | 4.5 ± 0.3 | |
| kcat/K0.5 (M−1.s−1) | 1,911 | 58 | - | |