Table 1. Effects of tyrosine and bromide on peptide nitration by eosinophil peroxidase.
Nitration of the peptide acetyl-Ser-Gln-Asn-Tyr-Pro-Val-Val (100 μM) was started by adding hydrogen peroxide (100 μM) to 20 nM eosinophil peroxidase and 100 μM nitrite, with or without additions of 10 μM tyrosine, 100 μM bromide, 100 μM thiocyanate or 1 mM methionine at 21 °C in 50 mM phosphate buffer (pH 7.4). Reactions were stopped after 1 h with 20 μg/ml catalase. Nitration of the peptide was measured by HPLC as outlined in the Experimental section. Results shown are means±S.D. for n experiments. EPO, eosinophil peroxidase; SCN−, thiocyanate.
| Reaction system | [Nitrated peptide] (μM) |
|---|---|
| Peptide alone | 0 |
| +EPO/H2O2/NO2− | 9.3±1.1 (n=6) |
| +Tyr | 14.1±0.4 (n=6) |
| +Br−/Met | 7.7±0.3 (n=4) |
| +Br−/Met/Tyr | 10.0±0.1 (n=4) |
| +SCN− | 2.2±1.3 (n=4) |