TABLE 1.
Kinetic constants of human DHRS3 + RDH10 versus RDH10 alone
Kinetic constants were determined using the same preparation of microsomes containing DHRS3 + RDH10, except for NADP+ Km value, which was obtained using a different preparation of microsomes. All kinetic measurements were repeated at least 3 times.
| Substrate/cofactor | Apparent Km | Apparent Vmax |
|---|---|---|
| μm | nmol min−1mg−1 | |
| DHRS3 + RDH10 | ||
| NADPH | 2.6 ± 0.8 | 2.9 ± 0.3 |
| 280 ± 230 | 2.3 ± 0.5 | |
| NADP+ | 7.8 ± 1.5 | 3.5 ± 0.3 |
| 740 ± 770 | 0.9 ± 0.4 | |
| NADH | 12 ± 4 | 3.5 ± 0.7 |
| 470 ± 280 | 7.8 ± 1.4 | |
| All-trans-retinaldehyde + NADPH | 0.15 ± 0.06 | 2.1 ± 0.5 |
| 6.8 ± 4.9 | 4.9 ± 0.9 | |
| All-trans-retinol + NADP+ | 0.029 ± 0.006 | 0.45 ± 0.03 |
| 3.9 ± 1.5 | 0.55 ± 0.06 | |
| All-trans-retinaldehyde + NADH | 0.24 ± 0.67 | 1.7 ± 4.4 |
| 3.2 ± 2.3 | 17 ± 3 | |
| 11-cis-retinaldehyde | NDa | |
| RDH10 | ||
| NADH | 11 ± 4 | 1.1 ± 0.1 |
| All-trans-retinol + NAD+ | 0.039 ± 0.013 | 0.55 ± 0.03 |
| All-trans-retinaldehyde + NADH | 0.46 ± 0.06 | 1.7 ± 0.1 |
| 11-cis-retinolb | 0.06 ± 0.01 | 1.42 ± 0.06 |
a ND, not detectable.
b Data from Ref. 17. The two sets of numbers represent two different forms of DHRS3 (in case of NADP(H) as cofactor) or two different forms of RDH10 (in case of NAD(H) as cofactor): one with higher affinities for retinoid substrates and cofactors, and the other, with lower affinities.