Characteristics of a Urate-Degrading Diamine Oxidase-Peroxidase Enzyme System in Soybean Radicles

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The cadaverine content of soybean radicles showed a maximum peak 3-4 days after planting. The variation coincided with radicle uricase activity during seed germination. The uricase activity could not be fractionate when the buffer pH for the extraction was at 6.0. The addition of 1 M KCl or NaCl to the buffer allowed the extraction of the uricase activity, but an addition of 1 M MgCl_2 or BaCl_2 inhibited this enzyme's activity. The urate-degrading enzyme system was purified 248-fold per milligram of protein from soybean radicles. The respective K_m values of the diamine oxidase activity for cadaverine and of the urate-degrading activity for hydrogen peroxide and urate were 1.25, 2.93 and 50.3μM. Analysis by gel electrophoresis of the partially purified enzyme fraction revealed that the urate-degrading enzyme system consisted of a peroxidase that degrades urate with hydrogen peroxide and a diamine oxidase that releases hydrogen peroxide. These data are evidence that a urate-degrading diamine oxidase and peroxidase system exists in soybean radicles and that the reaction rate of urate-degradation is controlled by the concentration of cadaverine.
日本植物生理学会の論文