FEBS Letters 2003-10-23

Enzymatic nitration of phytophenolics: evidence for peroxynitrite-independent nitration of plant secondary metabolites.

Yasuko Sakihama, Ryoko Tamaki, Hisashi Shimoji, Toshio Ichiba, Yukiharu Fukushi, Satoshi Tahara, Hideo Yamasaki

Index: FEBS Lett. 553(3) , 377-80, (2003)

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Abstract

Peroxynitrite (ONOO(-)), a reactive nitrogen species, is capable of nitrating tyrosine residue of proteins. Here we show in vitro evidence that plant phenolic compounds can also be nitrated by an ONOO(-)-independent mechanism. In the presence of NaNO(2), H(2)O(2), and horseradish peroxidase (HRP), monophenolic p-coumaric acid (p-CA, 4-hydroxycinnamic acid) was nitrated to form 4-hydroxy-3-nitrocinnamic acid. The reaction was completely inhibited by KCN, an inhibitor for HRP. The antioxidant ascorbate suppressed p-CA nitration and its suppression time depended strongly on ascorbate concentration. We conclude that nitrogen dioxide radical (NO(2)(radical)), but not ONOO(-), produced by a guaiacol peroxidase is the intermediate for phytophenolic nitration.