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Microsomal preparations of white lupin ( Lupinus albus ) radicles and cell suspension cultures catalyse the prenylation of positions 6, 8 and 3′ of the isoflavones genistein and 2′-hydroxygenistein. Both the substrates and the enzyme reaction products are natural constituents of lupin tissues. Enzymatic prenylation of isoflavones required dimethylallyl pyrophosphate (DMAPP) and 12 mM Mn 2+ with optimum activity at pH 7.5 in Tris-HCl buffer. The apparent K m values for DMAPP and the prenyl acceptors were 4 and 5 μM, respectively. Isopentenyl pyrophosphate was a competitive inhibitor of the prenylation reaction, with an apparent K i of 5 μM. The bulk of enzymatic activity was associated with the membrane fraction and could only be solubilized in the presence of a detergent. The differences observed in prenyltransferase activity ratios, in relation to the source of the enzyme and the type of detergent used, suggest that prenylation at positions 6, 8 and 3′ of isoflavones is catalysed by a number of distinct enzymes.

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 °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 μkat/kg protein.

A prenyltransferase activity (EC 2.5.1.1) has been partially purified from the flavedo of Citrus sinensis with 30–40-fold purification and 35–60 % yield. The enzyme catalyses the condensation of IPP with DMAPP or GPP. The products are neryl and geranyl pyrophosphate as well as (2 E ,6 E )- and (2 Z ,6 E )-farnesyl pyrophosphate. The two C 15 -products are predominant. The E - and Z -synthetase activities are partially dissociated during the purification procedure, as well as by heat or ageing. Preparations devoid of Z -synthetase were obtained. Mg 2 + is required for full activity. Mn 2 + or Co 2 + can replace Mg 2 + . The ratio of E/Z -products formed is different for each cation. Mg 2 + complexes of allylic substrates or of products protect the enzyme against heat-inactivation and against inactivation by DTNB. The results are interpreted in terms of two or more prenyltransferases stereoselective for the synthesis of E - and Z -products.