Fr Francium

Isoprenoids form the largest family of compounds found in nature. Isoprenoids are often attached to other moieties such as aromatic compounds, indoles/tryptophan, and flavonoids. These reactions are catalyzed by three phylogenetically distinct prenyltransferases: soluble aromatic prenyltransferases identified mainly in actinobacteria, soluble indole prenyltransferases mostly in fungi, and membrane-bound prenyltransferases in various organisms. Fusicoccin A (FC A) is a diterpene glycoside produced by the plant-pathogenic fungus Phomopsis amygdali and has a unique O-prenylated glucose moiety. In this study, we identified for the first time, from a genome database of P. amygdali, a gene (papt) encoding a prenyltransferase that reversibly transfers dimethylallyl diphosphate (DMAPP) to the 6′-hydroxy group of the glucose moiety of FC A to yield an O-prenylated sugar. An in vitro assay with a recombinant enzyme was also developed. Detailed analyses with recombinant PAPT showed that the enzyme is likely to be a monomer and requires no divalent cations. The optimum pH and temperature were 8.0 and 50 °C, respectively. K_m values were calculated as 0.49±0.037 μM for FC P (a plausible intermediate of FC A biosynthesis) and 8.3±0.63 μM for DMAPP, with a k_cat of 55.3±3.3×10⁻³ s. The enzyme did not act on representative substrates of the above-mentioned three types of prenyltransferase, but showed a weak transfer activity of geranyl diphosphate to FC P.

A novel sugar prenyltansferase, PAPT, from the fungus Phomopsis amygdali has been cloned and characterized. This enzyme transfers dimethylallyl diphosphate to the 6′-hydroxy group of the glucose moiety of fusicoccin (FC) A, a diterpene glucoside. To the best of our knowledge, this is the first enzyme to catalyze prenylation of a hydroxyl group in a glucose moiety.