ENZYMIC GLUCOSYLATION OF THE CYTOKININ, 6-BENZYLAMINOPURINE

Two separate enzyme activities for the formation of the 7- and 9-glucopyranosyl derivatives of the cytokinin 6-benzylaminopurine (BAP), have been found in soluble extracts of expanded cotyledons of radish (Raphanus sativus). The enzymes have been purified partially by column chromatography on DEAE-cellulose. Each activity results in formation of both glucosides, and the enzymes use UDP-glucose as the source of the glucose residue. A sensitive radiotracer assay was necessary to detect maximum specific activities of a few nmol h-1 g-1 of tissue. The results presented indicate that these enzymes are responsible for the formation of glucosides from BAP when it is fed to radish seedlings in aqueous solution, and may also form zeatin-7-glucoside, a naturally-occurring cytokinin. © 1979.