Table 2.
Trypanothione reductase spectral properties and kinetic parameters. Km values for T(S)2 were determined for TbTryR and TcTryR in both the 340 and 412 nm assays. Additional data from L. donovani[29] and T. cruzi[12,31].
| Parameter | Units | T. b. brucei | T. cruzi | L. donovani |
|---|---|---|---|---|
| Spectral properties | ||||
| λmax (oxidised enzyme) | nm | 463 | 464 | 463 |
| ɛ0 at λmax | mM−1 cm−1 | 11.4 ± 0.3 | 11.4 | 11.5 |
| Charge transfer band (reduced enzyme) | – | Yes | Yes | Yes |
| ɛ0 at λ530 nm | mM cm−1 | 4.1 | 4.9 | 4.2 |
| Enzymatic properties | ||||
| Specific activity | U mg−1 | 91 | 143 | 113 |
| Km NADPH (by DTNB-coupled assay) | μM | 0.77 ± 0.01 | n.d.a | n.d.a |
| Km T(S)2 (by DTNB-coupled assay) | μM | 2.35 ± 0.07 | 10.4 ± 0.3 | n.d.a |
| Km T(S)2 (by NADPH oxidation) | μM | 6.9 ± 0.7 | 29.6 ± 2.8 | 36 |
| kcat (by NADPH oxidation) | s−1 | 46.8 ± 1.1 | 77 ± 8.0 | 179 |
| kcat/Km | M−1 s−1 | 8.7 × 106 | 2.6 × 106 | 5 × 106 |
a
n.d.: not determined.