title: Characterization of peroxidase in buckwheat seed.
abstract: A peroxidase (POX)-containing fraction was purified from buckwheat seed. The POX consisted of two isozymes, POX I and POX II, that were purified 6.6- and 67.4-fold, respectively. Their molecular weights were estimated to be 46.1 kDa (POX I) and 58.1 kDa (POX II) by gel filtration. While POX I and II each oxidized quercetin, o-dianisidine, ascorbic acid and guaiacol, only POX II oxidized ABTS. Kinetic studies revealed that POX I and II had lower K(m) values for quercetin (0.071 and 0.028 mM), ABTS (0.016 mM for POX II) and ascorbic acid (0.043 and 0.029 mM) than for o-dianisidine (0.229 and 0.137 mM) and guaiacol (0.288 and 0 ). The optimum pHs of POX I and II for various substrates were almost the same, except for quercetin; pH 8.0 for POX I and pH 4.5 for II. Their optimal temperatures were 30 degrees C (POX I) and 10 degrees C (POX II), and POX I was more stable than POX II above 30 degrees C.
authors.affiliation: National Agriculture Research Center for Hokkaido Region, Shinsei, Memuro, Kasai, Hokkaido 082-0071, Japan. tsuzu@affrc.go.jp
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Suzuki
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Honda
authors.forename: Yuji
authors.initials: Y
authors.lastname: Mukasa
authors.forename: Sun-Ju
authors.initials: SJ
authors.lastname: Kim
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry / Q000378:metabolism; D052160:Benzothiazoles; D003962:Dianisidine / Q000737:chemistry / Q000378:metabolism; D004795:Enzyme Stability; D019612:Fagopyrum / Q000201:enzymology*; D006139:Guaiacol / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D009195:Peroxidase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D011794:Quercetin / Q000737:chemistry / Q000378:metabolism; D012639:Seeds / Q000201:enzymology; D013451:Sulfonic Acids / Q000737:chemistry / Q000378:metabolism; D013696:Temperature; D014018:Tissue Distribution
chemical_list: D052160:Benzothiazoles; D007527:Isoenzymes; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D006139:Guaiacol; D011794:Quercetin; D009195:Peroxidase; D003962:Dianisidine; D001205:Ascorbic Acid