Chem. Res. Toxicol. 2001, 14, 459
Additions and Corrections A Novel Procedure for Generating both Nitric Oxide and Superoxide in Situ from Chemical Sources at Any Chosen Mole Ratio. First Application: Tyrosine Oxidation and a Comparison with Preformed Peroxynitrite [Volume 13, Number 12, December 2000, pp 1287-1293] GEORGE R. HODGES,* JASVIR MARWAHA, TOMAS PAUL,* AND K. U. INGOLD* Page 1292. The last three sentences in the Discussion are incorrect and should be replaced with the following: Furthermore, a report on CO2 enhancement of peroxynitritemediated tyrosine nitration in plasma proteins (37) was subsequently misinterpreted to imply that the peroxynitriteCO2 adduct, or a product derived from it, was not very reactive toward sulfhydryls (38). Although the peroxynitrite/ CO2/sulfhydryl/tyrosine system had not been examined originally (37), this misinterpretation was used to argue against a role for radicals in this nitration (38). In fact, CO3•- reacts more rapidly with Tyr (Table 1) than with cysteine [k ) 3.2 × 105 M-1 s-1 (39)]. Nevertheless, we have found that cysteine protected Tyr from nitration by preformed peroxynitrite and CO2, just as was reported earlier for the antioxidants urate and ascorbate (37). Interestingly, this level of protection by cysteine was 3 times greater than that calculated assuming that it acted solely as a competitive scavenger for CO3•-. This is due to facile reduction of phenoxyl radicals by cysteine (40), leading to a diminution of all Tyr-O•-derived products. 10.1021/TX010500L Published on Web 03/08/2001
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