Table 4.
Principal oxidative and reductive steroidogenic reactions catalyzed by 17βHSD types 1–6
| 17βHSD type | Type 1 | Type 2 | Type 3 | Type 4 | Type 5 | Type 6 |
|---|---|---|---|---|---|---|
| Other names | AKR1C3 | RODH | ||||
| Preferred direction | Reduction | Oxidation | Reduction | Oxidation | Reduction | Oxidation |
| Favored cofactor in intact cells | NADPH | NAD+ | NADPH | NAD+ | NADPH | NAD+ |
| Estrone → estradiol | Major | Minor | ||||
| Estradiol → estrone | Major | Trace | ||||
| 16OH-estrone → estriol | Major | |||||
| Estriol → 16OH-estrone | Major | Trace | ||||
| DHEA → androstenediol | Modest | Modest | ||||
| Androstenedione → testosterone | Trace | Major | Minor | |||
| Testosterone → androstenedione | Major | Trace | ||||
| DHT → 5α-androstane-3,20dione | Major | Trace | Modest | |||
| 5α-Androstane-3,20dione → DHT | Major | |||||
| DHT → 5α-androstane-3α,17βdiol | Modest | |||||
| 5α-Androstane-3α,17βdiol → DHT | Modest | |||||
| 5α-Androstane-3α,17βdiol → androsterone | Modest | |||||
| Androsterone → 5α-androstane 3,20dione | Modest |
These enzymes catalyze other reactions as well: 17βHSD6 (RODH) also acts as an isomerase with modest activity to convert 5α-androstane 3α,17βdiol to 5α-androstane 3β,17βdiol and androsterone to 3β-androsterone. © W. L. Miller and R. J. Auchus.