Table 2. Second-order rate constants for reaction of two-electron oxidants with selenium-containing compounds and enzymes.
Data for radical-mediated oxidation reactions are given in [18,45,46]. Values were determined at room temperature (20–25°C) and pH 7.0–7.4 unless stated otherwise. PC-OOH, phosphatidylcholine hydroperoxide.
| Substrate | Oxidant | k2 (M−1·s−1) | Reference |
|---|---|---|---|
| Sec | HOSCN | 1.24×106 | The present study |
| Selenocysteine methyl ester | HOSCN | 3.7×106 | The present study |
| Selenocystamine | H2O2 | 9.7×102 | [29] |
| t-BOOH | 1.2×102 | [29] | |
| Cumene-OOH | 2.5×102 | [29] | |
| HOSCN | 5.8×106 | The present study | |
| 3-Selenopropionic acid | HOSCN | 2.0×106 | The present study |
| Gly-Sec-Gly | HOSCN | 1.65×106 | The present study |
| γ-Glu-Sec-Gly | HOSCN | 1.7×106 | The present study |
| SeMet | ONOOH | 2.4×103 | [30] |
| HOSCN | 2.8×103 | The present study | |
| Fmoc—SeMet | HOSCN | 1.2×104 | The present study |
| Selenomethylcysteine | HOSCN | <500 | The present study |
| Ebselen | H2O2 | 4.8 | [47] |
| ONOOH | 2×106 (25°C, pH≥8) | [48] | |
| HOSCN | ~30 | The present study | |
| Ebselen–GSH conjugate (selenosulfide) | H2O2 | <0.17 | [47] |
| Ebselen selenol | H2O2 | 47 | [47] |
| >350 | [49] | ||
| 2.05×102* | [50] | ||
| Ebselen diselenide | H2O2 | 5.3 | [47] |
| 2-(Methylseleno)benzanilide | ONOOH | 2.7×103 | [51] |
| GPx1 (per tetramer) | H2O2 | 4.1×107† | [52] |
| t-BOOH | 4.2×106† | [52] | |
| ONOOH | 8.0×106 | [53] | |
| ONOOH | 1.8×105 (37°C, pH 7.1) | [31] | |
| HOSCN | 5×105 | The present study | |
| Oxidized GPx1 (per tetramer) | ONOOH | 7.4×105 | [53] |
| Extracellular GPx | H2O2 | 4.0×107† | [52] |
| t-BOOH | 2.3×106† | [52] | |
| PC-OOH | 3.4×105† | [52] | |
| Phospholipid hydroperoxide GPx4 | PC-OOH | 1.5×107† | [52] |
| Selenoprotein P | PC-OOH | 8.6×104† | [52] |
*Measured under catalytic conditions in the presence of dehydrolipoate as a cofactor with the tetrameric enzyme; these values are therefore not strictly comparable with direct rate constant data.
†Measured under catalytic conditions in the presence of GSH as a cofactor with the tetrameric enzyme; these values are therefore not strictly comparable with direct rate constant data.