TABLE 2.
Kinetic constants for DoxA substratesa
| DoxA substrateb | Vmax (pmol · min−1 · mg−1) | Km (μM) | kcat (s−1) | kcat/Km (M−1 · s−1) |
|---|---|---|---|---|
| DOD | 1,600 ± 100 | 1.1 ± 0.1 | 2.4 × 10−2 ± 2 × 10−3 | 22,000 ± 1,000 |
| DHD | 3,900 ± 100 | 4.6 ± 1.0 | 6.3 × 10−1 ± 1 × 10−2 | 14,000 ± 2,000 |
| DAU | 7.5 ± 0.1 | 0.9 ± 0.1 | 1.2 × 10−4 ± 1 × 10−5 | 130 ± 10 |
| DHC | 19 ± 0.7 | 2.5 ± 0.9 | 2.6 × 10−4 ± 1 × 10−4 | 280 ± 10 |
a
Data represent kinetics based on total DoxA present in the assays. Our estimate, based on P-450 heme quantitation, is that approximately 20% of the enzyme is in the active form. Data presented represent the means of four data points ±1 standard deviation.
b
Abbreviations: DOD, 13-deoxydaunorubicin; DHD, 13-dihydrodaunorubicin; DAU, daunorubicin, DHC, 13-dihydrocarminomycin.