Direct comparisons of HFLM and HALM-catalyzed 4-hydroxylation of RAs to 4-hydroxylated metabolites1-a
| Enzyme Source | Substrate | 4-OH-RA | 4-oxo-RA |
|---|---|---|---|
| pmol/min/mg protein | |||
| HFLM | tRA | 587 ± 23 | 106 ± 68 |
| HALM | tRA | 105 ± 24 | 38 ± 7 |
| HFLM | 9cRA | 1596 ± 172 | 343 ± 12 |
| HALM | 9cRA | 143 ± 75 | 35 ± 5 |
| HFLM | 13cRA | 291 ± 74 | 131 ± 43 |
| HALM | 13cRA | 38 ± 19 | 55 ± 18 |
↵1-a RA substrates (7 μM) were preincubated with microsomes at 37°C for 3 min. Gestational age of HFLM was 109 days. Reactions were initiated by additions of NADPH (1 mM) and were continued for 10 min. Experiments were conducted in a darkened room with only yellow light to prevent both photoisomerization and autoxidation. For details, see Materials and Methods.