The first prenylation step in hyperforin biosynthesis
2005
Boubakir, Z. | Beuerle, T. | Liu, B. | Beerhues, L.
Prenylation reactions contribute considerably to the diversity of natural products. Polyprenylated secondary metabolites include hyperforin which is both quantitatively and pharmacologically a major constituent of the medicinal plant Hypericum perforatum (St. John's wort). Cell cultures of the related species Hypericum calycinum were found to contain a prenyltransferase activity which is likely to catalyze the first prenylation step in hyperforin biosynthesis. The enzyme was soluble and dependent on a divalent cation, with Fe(2+) leading to maximum activity (K(m) = 3.8 mM). The preferred prenyl donor was DMAPP (K(m) = 0.46 mM) and the preferred prenyl acceptor was phlorisobutyrophenone (K(m) = 0.52 mM). A broad pH optimum from 6.5 to 8.5 and a temperature optimum from 35 to 40 degrees C were observed. The formation of hyperforins in H. calycinum cell cultures was preceded by an increase in dimethylallyltransferase activity, with the maximum specific activity being 3.6 microkat/kg protein.
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