Isoprenoids microbial hydroxylation

Another derivative is the zeatin. Zeatin belongs to the plant-growth hormones, cytokinins. Cytokinins are adenine derivatives with isoprenoid side chain [108, 109]. The rate-limiting step of tra/is-zeatin biosynthesis is catalyzed by adenylate-isopentenyltransferase (cytokinin synthase) [110]. The plant enzyme (EC 2.5.1.27) utilize ADP, which is different from the microbial one (EC 2.5.1.112) which recognizes ATP/or ADP [111, 112]. Afterward, the adenylate-isopentenyl converts to the active tra/is-zeatin by a single hydroxylation reaction (cytokinin tra/is-hydroxylase). On the opposite site, cis-zeatin biosynthesis starts with a different transferase, tRNA-dimethylallyl-transferase (EC 2.5.1.75) [113-116], which mediates the transfer of an isopentenyl group of DMAPP to adenine of tRNAs. 

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