Hypochlorous acid (HOCl), generated by myeloperoxidase from H2O2 and Cl-, plays an important role in host defense and inflammatory tissue injury. We have studied the reaction of 3′,5′-di-O-acetyl-2′-deoxyguanosine with reagent HOCl and with a human myeloperoxidase-H2O2-Cl- system in order to characterize polar reaction products. When 100 μM 3′,5′-di-O-acetyl-2′-deoxyguanosine was reacted with 100 μM HOCl at pH 7.4 and 37°C and the reaction was terminated by N-acetylcysteine, 3′,5′-di-O-acetyl derivatives of previously reported products, such as diastereomers of spiroiminodihydantoin nucleoside, a diimino-imidazole nucleoside, an amino-imidazolone nucleoside, and 8-chloro-2′-deoxyguanosine were formed. In addition, we report the formation of 3′,5′-di-O-acetyl derivatives of a guanidinohydantoin nucleoside, an iminoallantoin nucleoside, and a diamino-oxazolone nucleoside in this system. The identification of the products was based on their identical ESI-MS and UV spectra and HPLC retention times with authentic compounds synthesized with other oxidation systems. All of these products were also formed in the reaction of 3′,5′-di-O-acetyl-2′-deoxyguanosine with the myeloperoxidase-H2O2-Cl- system under mildly acidic conditions. The yields of the products were greatly affected by the pH of the reaction mixture. The total yields of these products formed by HOCl at pH 7.4 and by the myeloperoxidase-H2O2-Cl- system at pH 4.5 were 72 and 43% of the consumed 3′,5′-di-O-acetyl-2′-deoxyguanosine, respectively, indicating that nearly half of the consumption of 3′,5′-di-O-acetyl-2′-deoxyguanosine by HOCl and the myeloperoxidase-H2O2-Cl- system can be accounted for by the formation of these products.
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