Dimethylallyl diphosphate: Kaempferol 8-dimethylallyl transferase in Epimedium diphyllum cell suspension cultures

Article abstract of DOI:10.1016/S0031-9422(96)00484-0

The enzymatic formation of des-O-methylanhydroicaritin from dimethylallyl diphosphate and kaempferol was investigated in the cell-free extract of Epimedium diphyllum cell suspension cultures. The enzyme catalysing the dimethylallyl group transfer to C-8 position of kaempferol (EC 2.5.1.) was membrane-bound and required divalent cations such as Mg²⁺ and Mn²⁺. Mg²⁺ was the most effective for the reaction. The enzyme showed a very broad pH optimum in the alkaline region, pH 7.5-11.0. It required dimethylallyl diphosphate as a sole prenyl donor, but had a rather broad substrate specificity for the prenyl acceptor. Not only kaempferol, but also quercetin (39%), apigenin (60%) and luteolin (34%) were prenylated, whereas kaempferol glycosides, naringenin and genistein were not prenylated. These results suggested that the prenylation reaction of kaempferol precedes the glycosylation step in epimedoside A biosynthesis. The apparent K(m) values for dimethylallyl diphosphate and kaempferol were 0.58 and 0.13 mM, respectively.