Enzymatic nitration of phytophenolics: evidence for peroxynitrite-independent nitration of plant secondary metabolites.
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.
Laboratory of Cell and Functional Biology, Faculty of Science, University of the Ryukyus, Nishihara, 903-0213 Okinawa, Japan.
Yasuko
Y
Sakihama
Ryoko
R
Tamaki
Hisashi
H
Shimoji
Toshio
T
Ichiba
Yukiharu
Y
Fukushi
Satoshi
S
Tahara
Hideo
H
Yamasaki
D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D003373:Coumaric Acids / Q000737:chemistry / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D009585:Nitrogen Dioxide / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000378:metabolism*; D010636:Phenols / Q000737:chemistry* / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D011190:Potassium Cyanide / Q000494:pharmacology; D013053:Spectrophotometry / Q000379:methods
D000975:Antioxidants; D003373:Coumaric Acids; D004791:Enzyme Inhibitors; D005609:Free Radicals; D009566:Nitrates; D009573:Nitrites; D010636:Phenols; D030421:Peroxynitrous Acid; D006735:Horseradish Peroxidase; C121048:guaiacol peroxidase; D009195:Peroxidase; D011190:Potassium Cyanide; D001205:Ascorbic Acid; D009585:Nitrogen Dioxide