Identification of a brevianamide F reverse prenyltransferase BrePT from Aspergillus versicolor with a broad substrate specificity towards tryptophan-containing cyclic dipeptides.

A putative brevianamide F reverse prenyltransferase gene brePT was amplified from Aspergillus versicolor NRRL573 by using primers deduced from its orthologue notF in Aspergillus sp. MF297-2 and overexpressed in Escherichia coli. The soluble His-tagged protein BrePT was purified to near homogeneity and assayed with tryptophan-containing cyclic dipeptides in the presence of dimethylallyl diphosphate. BrePT showed much higher flexibility towards its aromatic substrates than NotF and accepted all of the 14 tested tryptophan-containing cyclic dipeptides. Structure elucidation of the enzyme products by NMR and MS analyses proved unequivocally the highly regiospecific reverse prenylation at C2 of the indole nucleus. K(M) values of BrePT were determined for its putative substrates brevianamide F and DMAPP at 32 and 98 μM, respectively. Average turnover number (k (cat)) at 0.4 s⁻¹ was calculated from kinetic data of brevianamide F and DMAPP. K(M) values in the range of 0.082-2.9 mM and k (cat) values from 0.003 to 0.15 s⁻¹ were determined for other 11 cyclic dipeptides. Similar to known fungal indole prenyltransferases, BrePT did not accept geranyl or farnesyl diphosphate as prenyl donor for its prenylation.