Table 1. Steady-State Parameters for CpIMPDH and hIMPDH2a.
|
CpIMPDH |
hIMPDH2 | ||
|---|---|---|---|
| parameter | NAD+ | APAD+b | NAD+ |
| kcat (s−1) | 2.6 ± 0.1 | 3.0 ± 0.04 | 0.39 ± 0.01c |
| KM IMP (μM) | 13 ± 3 | ndd | 4 ± 1c |
| KM dinucleotide (μM) | 140 ± 10 | 190 ± 9 | 6 ± 1c |
| Kii dinucleotide (mM)e | 4.9 ± 0.5 | naf | 0.59 ± 0.02c |
| kcat/KM IMP (M−1 s−1) | (2.0 ± 0.5) × 105 | ndd | (9.8 ± 1.4) × 104 c |
| kcat/KM dinucleotide (M−1 s−1) | (1.9 ± 0.2) × 104 | (1.6 ± 0.1) × 104 | (6.5 ± 0.5) × 104 c |
| D2Okcat | 2.6 ± 0.1 | 3.3 ± 0.1 | 1.8 ± 0.1 |
a
Experimental conditions: 50 mM Tris-HCl, pH 8.0, 100 mM KCl, and 1 mM DTT at 25 °C.
b
APAD+ varied at saturating IMP (500 μM).
c
Values from ref 24.
d
Not determined.
e
Intercept inhibition constant describing uncompetitive inhibition, nomenclature of Cleland (48).
f
Not applicable.