Dose-response with Isolated enzymes

It is known that RNA polymerase I is associated in animal cells with protein kinase, which phosphorylates RNA-polymerase and induces an increase of its activity [20]. RNA polymerase I isolated from barley leaf chromatin is also associated with protein kinase activity [19], which is dramatically increased by the addition of BA into the reaction medium (Fig. 1). The dose response curve of this effect was typical of other phytohormone-induced reactions. The effect was specific for biologically active cytokinins (Z, kinetin, BA) and could not be demonstrated with their non-active analogues, adenine or 6-methyladenine. These results were confirmed in experiments with RNA-polymerase I and II isolated from nuclei of lupin cotyledons. Both enzymes possessed low protein kinase activity, but this was increased in vitro 10-fold by BA. 

Fig. 7.7. (A) Dose-response curve of the production of ribonuclease by aleurone layers at different concentrations of GA. Enzyme activity was measured in the medium and an extract of the tissue after 48 h incubation of the isolated aleurone layers. (B) Time course of ribonuclease production by 10 aleurone layers incubated with 5nM GA. Ar-rowed is the time of a-amylase release (see Figure 7.1 A). After Chrispeels and Varner, 1967 [22]...

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