Table 2.
Regioselectivity in CYP24A1-expressing cells
| Cell line | Substrate | Substrate concentration, nM* | C24/C23 activity ratio† | Ratio of peaks 2/7 or 2a/7a |
|---|---|---|---|---|
| V79-CYP24 | 1α,25-(OH)2D3 | 10,003 | 24.06 | 6.66 |
| V79-CYP24 | 1α,25-(OH)2D3 | 1,003 | 6.07 | — |
| OK | 1α,25-(OH)2D3 | 5,003 | 0.04 | 0.04 |
| OK | 1α,25-(OH)2D3 | 503 | 0.44 | — |
| V79-4/wt‡ | 1α,25-(OH)2D3 | 753 | 8.20 | 6.18 |
| V79-4/wt‡ | 1α,25-(OH)2D3 | 3 | 8.10 | — |
| V79-4/A326G‡ | 1α,25-(OH)2D3 | 753 | 0.12 | 0.12 |
| V79-4/A326G‡ | 1α,25-(OH)2D3 | 3 | 0.57 | — |
| V79-CYP24 | 25-OH-D3 | 10,003 | 4.60 | 2.83 |
| V79-CYP24 | 25-OH-D3 | 1,003 | 8.04 | — |
| OK | 25-OH-D3 | 5,003 | 0.08 | 0.10 |
| OK | 25-OH-D3 | 503 | 0.01 | — |
| V79-4/wt‡ | 25-OH-D3 | 753 | 4.83 | 3.70 |
| V79-4/wt‡ | 25-OH-D3 | 3 | 3.83 | — |
| V79-4/A326G‡ | 25-OH-D3 | 753 | 0.05 | 0.08 |
| V79-4/A326G | 25-OH-D3 | 3 | 0.70 | — |
All peak ratios for substrate 1α,25-(OH)2D3 refer to peaks 2/7. All peaks ratios for substrate 25-OH-D3refer to peaks 2a/7a. —, not applicable.
*Using [1β-3H]1α,25-(OH)2D3or [26,27-3H]25-OH-D3 (sp. activities in text).
†Ratio after summation of weighted products from either C24- or C23-hydroxylation pathways by using the method described in Materials and Methods.
‡V79-4 cells transfected with wild-type (wt) or A326G-mutated hCYP24A1.