Enzyme synthesis cytokinins

The second and main biosynthetic pathway of cytokinins in plants is de novo synthesis from phosphorylated adenosine and a precursor of the side chain. Fig. (2). The first and for a long time the only known genes encoding cytokinin de novo synthesizing enzyme, adenylate dimethylallyltransferase (EC 2.5,1.27) also called isopentenyltransferase... 

In planta, the CKX activity is affected by molecular components of the local metabolic resource pool that can serve as electron acceptors directly or after oxidative modification [72]. Favorable redox environment in cell or in the apoplast may allow the enzyme to work at maximum rate. However, it is still questionable, how its high catalytic power is used and if really needed for the depletion of active cytokinins in vivo. The most active CKX enzymes, AtCKX2 and AtCKX4 in Arabidopsis, act on the cytokinins in apoplast, where the concentration of cytokinins reflects the balance of accumulation via local synthesis and transport. 

A final exciting approach is to introduce into plants the genes for overproduction of a hormone, or antisense genes for an enzyme involve in hormone synthesis. These transgenic plants have already provided us with important information about the biological roles of auxins, cytokinins and ethylene [32]. 

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