A flavoprotein(FAD). Catalyses the oxidation of cytokinins, a family of N6-substituted adenine derivatives that are plant hormones, where the substituent is a dimethylallyl or other prenyl group. Although this activity was previously thought to be catalysed by a hydrogen-peroxide-forming oxidase, this enzyme does not require oxygen for activity and does not form hydrogen peroxide. 2,6-Dichloroindophenol, methylene blue, nitroblue tetrazolium, phenazine methosulfate and Cu(II) in the presence of imidazole can act as acceptors. This enzyme plays a part in regulating rice-grain production, with lower levels of the enzyme resulting in enhanced grain production .
Hedw., wild type and transgenic cells expressing the AtCKX2 gene from Arabidopsis thaliana, expression of AtCKX2 results in a significant decrease of cytokinin level and morphological changes such as altered morphology of filaments, impaired budding, and loss of sexual reproductivity
PsCKX1; L. cv. Sparkle, wild type and R50 carrying a recessive sym16 which is a pleiotropic mutant of pea which develops few, pale nodules and has pale young leaves, R50 has reduced CKX activity and increased cytokinin level compared with wild type, sequencing of DNA from both strains did not show any obvious mutations within the gene