TABLE 1.
Parameters from the kinetics of wild-type and mutant forms of pFBPases and wild typelFBPase
Values in parenthesis are standard deviations in the last significant digit.
| Specific activitya | Km Fru-1,6-P2b | Hill coefficient Mg2+c | Ka Mg2+d | Hill coefficient AMPe | Ki AMPf | Ki Fru-2,6-P2g | |
|---|---|---|---|---|---|---|---|
| μmol s−1 mg−1 | μm | mm | μm2 | μm | |||
| WT pFBPase | 25 (1) | 1.47 (7) | 1.7 (1) | 0.70 (5) | 2.2 (1) | 0.76 (8) | 0.14 (1) |
| S45H pFBPase | 11.9 (7) | 1.07 (7) | 1.6 (1) | 1.0 (1) | 1.8 (1) | 0.35 (5) | 0.053 (9) |
| T46R pFBPase | 12.3 (9) | 0.68 (8) | 1.8 (2) | 0.93 (9) | 2.4 (2) | 4.8 (2) | 0.27 (5) |
| L186Y pFBPase | 21.0 (7) | 1.1 (1) | 1.6 (1) | 0.68 (4) | 1.7 (2) | 0.58 (9) | 0.16 (1) |
| Cav− pFBPase | 15.2 (9) | 1.1 (2) | 1.8 (1) | 0.82 (6) | 2.2 (2) | 0.56 (4) | 0.14 (1) |
| lFBPase | 15 (1) | 1.0 (1) | 0.77 (8) | 1.3 (1) | 2.2 (2) | 0.58 (5) | 0.05 (1) |
a Determined at saturating Fru-1,6-P2 (20 μm) and saturating Mg2+ (5 mm for wild-type pFBPase and lFBPase and 10 mm for mutant pFBPases). Reported values come from five repetitions.
b Determined at saturating Mg2+ (5 mm for wild-type pFBPase and lFBPase and 10 mm for mutant pFBPases). The concentrations of Fru-1,6-P2 vary from 0.3 to 20 μm.
c Hill coefficient for Mg2+ employed 0.2–20 mm Mg2+ and saturating Fru-1,6-P2 (20 μm).
d Determined by using concentrations in Mg2+ from 0.5 to 5 mm and Fru-1,6-P2 from 0.5 to 10 μm.
e Determined by using concentrations in AMP from 0.1 to 100 μm and saturating Fru-1,6-P2 (20 μm) and Mg2+ (10 mm).
f Determined by using concentrations in Mg2+ from 0.5 to 5 mm with saturating Fru-1,6-P2 (20 μm). AMP concentrations range from 0 to 5 μm for wild-type pFBPase and lFBPase, from 0 to 3 μm for His45 pFBPase, from 0 to 20 μm for Arg46 pFBPase, and from 0 to 5 μm for Tyr186 and Cav− pFBPases.
g Determined by using Mg2+ (5 mm for wild-type pFBPase and lFBPase and 10 mm for mutant pFBPases) and Fru-1,6-P2 concentrations from 0.5 to 10 μm. Concentrations of Fru-2,6-P2 range from 0 to 1 μm for wild-type pFBPase, from 0 to 0.5 μm for His45 pFBPase and lFBPase, from 0 to 1 μm for Arg46 pFBPase, and from 0 to 1 μm for Tyr186 pFBPase and Cav− pFBPases.