Table 1.
InsP6 phosphatase (phytase) activity of MINPP
Enzyme | Km (μM) | Vmax (nmol/mg/min) |
---|---|---|
W.T. avian MINPP | 140 ± 12 | 715 ± 31 |
Q78A avian MINPP | 60 ± 2 | 625 ± 13 |
T27G avian MINPP | 92 ± 2 | 30 ± 0.4 |
W.T. human MINPP | 90 ± 1 | 6.2 ± 0.4 |
The kinetic parameters are for the hydrolysis of Mg–InsP6. These data were determined as described in Section 2. Most previous studies have used Na–InsP6 as a substrate. Thus, for comparative purposes, we determined the kinetic parameters of wild-type enzyme against Na–InsP6: the Km value was 200 ± 6 μM. The Vmax value was 501 ± 14 nmol/mg/min. All data represent means and standard errors from four experiments.