Cell free biosynthesis of cyto kinins in cultured tobacco nicotiana tabacum cultivar xanthi cells

Nishinari, N.; Syono, K.

Zeitschrift fuer Pflanzenphysiologie 99(5): 383-392


Accession: 004891885

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Cell-free biosynthesis of free cytokinins not related to the degradation of tRNA was demonstrated by using enzyme preparation extracted from cultured tobacco (N. tabacum cv. Xanthi) cells. The reaction mixture for cytokinin biosynthesis contained 20 mM Tris-HCl buffer (pH 7.6), 5 mM magnesium acetate, 0.5 mM isopentenylpyrophosphate, 50 .mu.M adenosine as a substrate and dialyzed enzyme extract. After 2.5 h of reaction at 27.degree. C, N6-(.DELTA.2-isopentenyl)adenosine, N6-(.DELTA.2-isopentenyl)adenine and trans-zeatin were biosynthetized. The radioactivity of [U-14C]adenosine was incorporated into these 3 cytokinins after 30 min of reaction in the cell-free system. From analyzing the time course of biosynthesis of cytokinins and the incorporation of [U14C]adenosine into cytokinins, it seems that the adenosine accepts the isopentenyl group directly to form N6-(.DELTA.2-isopentenyl) adenosine. This is converted to trans-zeatin via N6-(.DELTA.2-isopentenyl)adenine by several enzymes.