TABLE 2.
Inhibition of peroxidogenesis by heavy metals and other agents
| Inhibitora | IC50b |
|---|---|
| Ag+ | 446 ± 36 nMc |
| Hg2+ | 568 ± 15 nM |
| Zn2+ | 185 ± 7 μM |
| Cd2+ | 452 ± 155 μM |
| Cr3+ | 515 ± 182 μM |
| Pb2+ | 890 ± 157 μMc |
| Cu2+ | 2.2 ± 1.1 mM |
| Co2+ | 5.4 ± 0.9 mM |
| Ni2+ | 5.9 ± 1.5 mM |
| F− | 9.8 ± 1.5 mM |
| FHPO3− | >10 mM |
| Mn2+ | >10 mM |
| Ca2+ | >10 mM |
a
In every case in which inhibition was observed, controls were performed to confirm that the agents were inhibiting streptococcal peroxidogenesis rather than directly decomposing H2O2 or inhibiting the enzymatic assay for detection of H2O2. Agents which failed these tests were excluded from analysis.
b
All values reported are means ± SD of three independent determinations.
c
To avoid precipitation with Cl−, the IC50 for this metal was determined in a medium in which NO3− was substituted for Cl−.