Table 1.
Kinetic parameters of (S)- and (R)-NNAL formation by recombinant SDR enzymes and normal human lung cellular fractions
| (S)-NNAL | (R)-NNAL | |||||
|---|---|---|---|---|---|---|
| Enzyme |
K
M
(mM) |
V
max
(nmol/min/mg protein) |
V
max/KM (µl/min/mg protein) |
K
M
(mM) |
V
max
(nmol/min/mg protein) |
V
max/KM (µl/min/mg protein) |
| HSD11β1a | 0.80 ± 0.0 | 2.01 ± 0.5 | 2.45 ± 0.7 | 1.10 ± 0.1 | 3.57 ± 0.8 | 3.17 ± 0.7 |
| HSD17β12a | 0.45 ± 0.2 | 0.53 ± 0.1 | 1.43 ± 0.6 | 0.91 ± 1.4 | 6.42 ± 2.1 | 7.15 ± 5.2 |
| HEK293 | 1.28 ± 0.9 | 0.88 ± 0.4 | 0.64 ± 0.5 | 0.73 ± 0.1 | 1.15 ± 0.6 | 1.61 ± 1.0 |
| AKR1C1b | 1.12 ± 0.2 | 100 ± 16 | 89.9 ± 3.2 | 1.39 ± 0.1 | 1.83 ± 0.1 | 1.33 ± 0.1 |
| AKR1C2b | 1.63 ± 0.1 | 23.9 ± 0.8 | 14.7 ± 1.1 | 3.79 ± 0.9 | 1.28 ± 0.1 | 0.35 ± 0.1 |
| AKR1C3b | 1.15 ± 0.3 | 24.4 ± 0.7 | 21.9 ± 5.0 | 0.62 ± 0.4 | 1.20 ± 0.9 | 1.95 ± 0.6 |
| AKR1C4b | 0.80 ± 0.1 | 10.4 ± 0.2 | 12.5 ± 1.5 | 2.33 ± 0.4 | 0.85 ± 0.1 | 0.37 ± 0.1 |
| CBR1† | 0.70 ± 0.1 | 72.5 ± 6.6 | 106 ± 28 | 0.53 ± 0.1 | 0.42 ± 0.1 | 0.82 ± 0.2 |
| Lung microsomesc | 1.98 ± 0.8 | 0.86 ± 0.4 | 0.46 ± 0.4 | 0.89 ± 0.3 | 6.27 ± 3.9 | 7.05 ± 3.1 |
| Lung cytosolc | 1.75 ± 1.0 | 4.11 ± 3.6 | 2.35 ± 0.5 | 4.93 ± 4.0 | 1.03 ± 1.2 | 0.27 ± 0.9 |
aFor the microsomal enzymes HSD11β1 and HSD17β12, Vmax values were normalized based on the expression of HSD11β1 as described in the Materials and Methods.
bFor the cytosolic enzymes (AKRs 1C1, 1C2, 1C3 and 1C4, and CBR1), Vmax values were calculated based on ng of purified cytosolic enzyme added to the reaction as described in the Materials and Methods.
c V max values were normalized relative to total protein as described in the Materials and Methods.