Tartary buckwheat is targeted as a healthy food because its food contains large amounts of polyphenols such as rutin and quercetin, especially. Quercetin is a substrate for POX activity, which sometimes plays important roles for quality changes in foods. Therefore, to obtain a basic understanding of the roles of Tartary buckwheat POX, we purified and characterized POX in Tartary buckwheat seeds. POX was purified (76.7 fold, final yield 4.77%). Tartary buckwheat seeds bore a single major POX (MW 46.8 kDa). Kinetic studies revealed that POX had lower K-m values for quercetin (0.32 mM) and o-dianisidine (0.316 mM) than for ABTS (1.86 mM) and guaiacol (0.958 mM). POX showed greater activity under acidic pH conditions. Optimum pH of POX was the same pH as Tartary buckwheat dough. In addition, optimum temperature was around 20 degrees C, corresponding to the temperature where dough is usually handled. Therefore, POX in Tartary buckwheat may play an important role in quality changes in food.