Table 3. Kinetic parameters of human wild-type and N46S/L266R DGUOK enzymes with the phosphate donor.
The values are determined with fixed concentrations of dG or dA (20 μM) and concentrations of ATP varied from 0.25 to 7.5 mM. The three controls were within the age range of patients. Conditions and analysis of data were as described in Table 2. Km is given in mM and Vmax is given in picomoles of dG or dA phosphorylated per hour per milligram of protein; Km1, Vmax1, n°1: (first value of Vmax/Km,app for the patient) data below 2.5 mM ATP; Km2, Vmax2, n°2: (second value of Vmax/Km,app for the patient) data above 2.5 mM ATP. Also shown is the percentage of the mean control value.
| ATP/dG | ATP/dA | |||||||
|---|---|---|---|---|---|---|---|---|
| Km,app | Vmax | Vmax/Km,app | Hill constant | Km,app | Vmax | Vmax/Km,app | Hill constant | |
| Controls (n=3) | ||||||||
| Mean | 1.5 | 1030 | 687 | 0.80 | 0.95 | 2066 | 2175 | 0.77 |
| Range | (1.4–1.7) | (706–1196) | (474–848) | (0.70–0.89) | (0.9–1.1) | (1697–2527) | (1786–2808) | (0.69–0.83) |
| Carriers | ||||||||
| Mother (N46S) | 1.1 | 474 | 431 (63%) | 0.83 | 0.95 | 1072 | 1128 (52%) | 0.67 |
| Father (L266R) | 1.3 | 348 | 268 (39%) | 0.83 | 1.0 | 696 | 696 (32%) | 0.88 |
| Brother (N46S) | 1.25 | 410 | 328 (48%) | 0.81 | 1.1 | 879 | 799 (37%) | 0.68 |
| Mother (c.763_766dupGATT) | 1.7 | 483 | 284 (41%) | 0.78 | 0.8 | 826 | 1032 (47%) | 0.86 |
| Patient | ||||||||
| Patient 1 (N46S, L266R) | Km1=0.45 | Vmax1=67 | n°1=149 (22%) | − | Km1=0.45 | Vmax1=134 | n°1=298 (14%) | − |
| Km2=4.5 | Vmax2=193 | n°2=43 (6%) | − | Km2=9.4 | Vmax2=489 | n°2=52 (2.4%) | − | |