Ralph R K, McCombs P J, Tener G, Wojcik S J
Biochem J. 1972 Dec;130(4):901-11. doi: 10.1042/bj1300901a.
Kinetin stimulated phosphorylation of protein in floated Chinese-cabbage leaf discs, but inhibited protein phosphorylation in nuclei+chloroplast extracts from Chinese-cabbage or tobacco leaves. Kinetin also inhibited protein phosphorylation in isolated tobacco nuclei or nuclei from carrot secondary-phloem tissue. Purified Chinese-cabbage leaf ribosomes exhibited protein kinase activity which was inhibited by kinetin and zeatin. The ribosome-associated kinase responded to kinetin and zeatin differently from that associated with nuclei+chloroplast preparations. Protein phosphorylation in vitro was not affected by adenosine 3':5'-cyclic monophosphate, indol-3-ylacetic acid or gibberellic acid. It was only inhibited by N(9)-unsubstituted purines, among which the known cytokinins were the most effective inhibitors. The results are discussed in relation to possible similarities between the effects of cytokinins in plant tissues and the effects of adenosine 3':5'-cyclic monophosphate in animal tissues. Both compounds appear to modify the activity of protein kinases and both affect many different cellular processes.
激动素刺激了漂浮的大白菜叶片圆片中蛋白质的磷酸化，但抑制了大白菜或烟草叶片的细胞核+叶绿体提取物中的蛋白质磷酸化。激动素还抑制了分离的烟草细胞核或胡萝卜次生韧皮部组织细胞核中的蛋白质磷酸化。纯化的大白菜叶片核糖体表现出蛋白激酶活性，该活性受到激动素和玉米素的抑制。核糖体相关激酶对激动素和玉米素的反应与细胞核+叶绿体制剂相关激酶不同。体外蛋白质磷酸化不受3':5'-环磷酸腺苷、吲哚-3-乙酸或赤霉素的影响。它仅被N(9)-未取代嘌呤抑制，其中已知的细胞分裂素是最有效的抑制剂。结合细胞分裂素在植物组织中的作用与3':5'-环磷酸腺苷在动物组织中的作用之间可能存在的相似性，对结果进行了讨论。这两种化合物似乎都能改变蛋白激酶的活性，并且都影响许多不同的细胞过程。
