大豆叶片衰老过程中质膜蛋白激酶自磷酸化状态和催化活性的变化

以大豆幼苗初生叶为材料研究了衰老过程中质膜蛋白激酶自磷酸化状态和催化活性的变化。结果发现质膜上一个57kD的蛋白激酶分子上有多个自磷酸化位点，而且自磷酸化反应能提高该酶催化组蛋白H1磷酸化的激酶活力。进一步的研究表明诱导衰老处理造成的57kD蛋白激酶自磷酸化状态的变化，可能对调节它在衰老过程中催化活性的变化起重要作用；而外源6-BA预处理则能够维持57kD蛋白激酶体内高自磷酸化状态，保持该激酶在衰老过程中的催化活力。对衰老和6-BA处理过程中质膜上39和47kD蛋白激酶自磷酸化状态变化的研究表明，这两种激酶可能参与大豆叶片对6-BA刺激信号的传导和/或应答反应过程。

Senescence-induced Changes in Autophosphorylation Status and CatalyticActivity of Plasma Membrane Protein Kinases in Soybean Primary Leaves

Here we report an experimental system involving soybean primary leaves which are highly sensitive to senescence inducing treatment (ST) and exogenous 6 BA application for the study of the mechanism of the retardation of leaf senescence. By using a modified method suggested by Ferrell and Martin (1991) for detecting autophosphorylation activity of protein kinases, as well as by using a protocol of in vitro prephosphorylation of the samples with unlabelled ATP, we studied the possible effect of autophosphorylation on catalytic activity of protein kinases associated with plasma membrane of soybean primary leaves. The results suggested that there were multiple sites on a 57 kD calcium dependent protein kinase (CDPK) molecule for autophosphorylation and that autophosphorylation could improve its catalytic activity in phosphorylating histone H1. ST induced changes in in vivo autophosphorylation status of the 57 kD CDPK may play an important role in regulating its catalytic activity during leaf senescence, and 6 BA pretreatment may make the high catalytic activity of this kinase longlasting. The effect of 6 BA application on ST induced changes of autophosphorylation activity of a 39 kD and a 47 kD protein kinases implied involvement of these two kinases in cytokinin stimulus/response cascade system.