Table 1. Kinetic characterization of Hsd4AMN from M. neoaurum ATCC 25795a.
| Hsd4AMN |
|||
|---|---|---|---|
| Substrateb | Vmax (μmol/min/mg) | Km(μM) | Co-factor |
| AD | n.d.c | n.d. | NADH |
| TS | 0.169 ± 0.052 | 23 ± 7 | NAD+ |
| ADD | n.d. | n.d. | NADH |
| BD | 0.217 ± 0.068 | 19 ± 4 | NAD+ |
| epi-TS | n.d. | n.d. | NAD+ |
| 17α-MT | n.d. | n.d. | NAD+ |
| 4-HBC | n.d. | n.d. | NAD+ |
| 1,4-HBC | n.d. | n.d. | NAD+ |
| acetoacetate | n.d. | n.d. | NADH |
| DL-β-hydroxybutyric acid | n.d. | n.d. | NAD+ |
| acetoacetyl-CoA | 0.091 ± 0.012 | 101 ± 27 | NADH |
| DL-β-hydroxybutyryl-CoA | 0.113 ± 0.025 | 124 ± 39 | NAD+ |
aThe maximal specific activity Vmax and substrate affinity constant Km are indicated as average ± standard error (n = 3). Hsd4AMN displayed distinct activities in distinct co-factor environments (NADH/NAD+), which is specified in the rightmost column. The activity of Hsd4AMN was determined by the rate of NAD+/NADH formation at 340 nm (ε = 6.22 mM−1 cm−1) and 30 °C.
bAbbreviations: AD, androst-4-ene-3,17-dione; TS, testosterone, ADD, androst-1,4-dien-3,17-dione; BD, boldenone; epi-TS, 4-androstene-17α-ol-3-one; 17α-MT, 4-androstene-17α-methyl-17β-ol-3-one; 4-HBC, 22-hydroxy-23,24-bisnorchol-4-ene-3-one; 1,4-HBC, 22-hydroxy-23,24-bisnorchol-1,4-dien-3-one.
cn.d., not detected.