高等植物叶片中的硝酸还原酶活性稳定因子

从小麦、油菜、浮萍、番茄、烟草的叶片中分离得到NR-SF。不同植物材料中NR及NR-SF能起交叉反应;不同NR-SF影响NR酶动力学性质相同;不同NR-SF的凝胶电泳谱带显示蛋白和糖蛋白性质。NR-SF广泛存在于植物细胞中。

THE STABILIZING FACTOR OF THE NITRATE REDUCTASE ACTIVITY FROM THE LEAVES OF THE HIGHER PLANTS

The purpose of this investigation was to determine whether the stabilizing factor of nitrate reductase activity (NR-SF) was distributed widely in plant cells. NR-SF was isolated from the leaf homogenate of the wheat, tomato, tobacco, duckweed and rape by the method described previously except that Sephadex G_(75) filtration was omitted. High activity of NR was observed, when NR-SF from the five different species were combined with leaf extracts from wheat and tomato. The activity of NR with NR-SF was 1.4 times as high as that of NR alone, but the enhancement of activity of NR in leaf extracts from wheat, rape and duckweed by tomato NR-SF was shown to be very significant. The incubation of NR from the wheat and the rape with the tomato NR-SF increased enzyme activity by 86% and 39% respectively. When NR from wheat leaves was mixed with wheat, tobacco and rape NRSF separately, its reaction rate was 5 to 8 times that of NR without NR-SF. In addition, the former gave lower K_m and higher V_(max) than the latter. Besides this, all the five NR-SF identified were glycoproteins. Thus, it was suggested that the NR-SF was widely distributed in plants.