A putative prenyltransferase gene, ftmPT1, was identified in the genome sequence of Aspergillus fumigatus. ftmPT1 was cloned and expressed in Escherichia coli, and the protein FtmPT1 was purified to near homogeneity and characterized biochemically. This enzyme was found to catalyse the prenylation of cyclo-L-Trp-L-Pro (brevianamide F) at the C-2 position of the indole nucleus. FtmPT1 is a soluble monomeric protein, which does not contain the usual prenyl diphosphate binding site (N/D)DXXD found in most prenyltransferases, and which does not require divalent metal ions for its enzymic activity. K m values for brevianamide F and dimethylallyl diphosphate were determined as 55 and 74 mM, respectively. The turnover number was 5?57 s "1 . FtmPT1 showed a high substrate specificity towards dimethylallyl diphosphate, but accepted different tryptophan-containing cyclic dipeptides. Together with dimethylallyltryptophan synthase of ergot alkaloid biosynthesis, FtmPT1 belongs to a new group of prenyltransferases with aromatic substrates. INTRODUCTIONTrans-prenyltransferases (Bohlmann et al., 1998;Liang et al., 2002;Sacchettini & Poulter, 1997) are involved in the biosynthesis of terpenoids from C-5 units. These enzymes usually contain one or more prenyl diphosphate binding motifs, (N/D)DXXD, in their sequences (Bohlmann et al., 1998;Liang et al., 2002;Sacchettini & Poulter, 1997). Their enzymic reaction depends strictly on the presence of metal ions such as Mg 2+ or Mn 2+ (Bohlmann et al., 1998;Liang et al., 2002). A special group of prenyltransferases catalyses the attachment of a prenyl moiety to an aromatic nucleus. These enzymes show similar sequence motifs and metal ion requirements to those of the trans-prenyltransferases. Examples of this group are the prenyltransferases involved in the biosynthesis of the primary metabolites ubiquinone (Turunen et al., 2004), menaquinone (Suvarna et al., 1998), tocopherol (Schledz et al., 2001) and plastoquinone (Collakova & DellaPenna, 2001), and the prenyltransferase involved in the formation of the plant secondary metabolite shikonin (Yazaki et al., 2002). All these enzymes are membrane-bound proteins.In contrast, the dimethylallyltryptophan synthase (DMATS) that catalyses the prenylation of tryptophan at position C-4 of the indole nucleus during ergot alkaloid biosynthesis in the fungus Claviceps has been found to be a soluble protein and is active in a metal-free buffer containing EDTA (Cress et al., 1981;Lee et al., 1976;Tsai et al., 1995; Tudzynski et al., 1999). Recently, two further soluble prenyltransferases with aromatic substrates, which are active in the absence of metal ions and contain no (N/D)DXXD motifs, CloQ involved in the biosynthesis of clorobiocin from Streptomyces roseochromogenes (Pojer et al., 2003) and LtxC involved in the biosynthesis of lyngbyatoxins from Lyngbya majuscula (Edwards & Gerwick 2004), have been identified. Very recently, we identified an orthologue of DMATS, FgaPT2, in the genome sequence of Aspergillus fumigatus (Unsöld & Li, 2005). Inte...

The genome sequence of Aspergillus fumigatus revealed the presence of a single hybrid polyketide synthase-non-ribosomal peptide synthetase (PKS/NRPS) gene that is present within a cluster of five genes suggestive of its involvement in secondary metabolism. Here, we present evidence that it is required for the biosynthesis of pseurotin A, a compound with an unusual heterospirocyclic gamma-lactam structure. We have confirmed that the genome reference strain A. fumigatus Af293 produces pseurotin A, a compound previously reported to be a competitive inhibitor of chitin synthase and an inducer of nerve-cell proliferation. Deletion or overexpression of the PKS/NRPS gene psoA in A. fumigatus leads to the absence or accumulation of pseurotin A, respectively; this indicates that this gene is essential for the biosynthesis of pseurotin A. It is likely that the first product of psoA is converted to pseurotin A by the products of other genes in this cluster.

A gene encoding a putative dimodular nonribosomal peptide synthetase (NRPS) was identified within a gene cluster of Aspergillus fumigatus, a species reported to produce fumitremorgins and other prenylated alkaloids. The gene was deleted and overexpressed in the genome reference strain Af293, and was also expressed in the naïve host Aspergillus nidulans, which lacks the equivalent gene cluster. While neither fumitremorgins nor the dipeptide brevianamide F (cyclo-L-Trp-L-Pro), an early intermediate, were detected in wild-type and deletion strains of A. fumigatus, brevianamide F accumulated in fungal cultures following increased expression of the NRPS gene in both A. fumigatus and A. nidulans. We conclude that the gene Afu8g00170, named ftmA, encodes the NRPS brevianamide synthetase. Brevianamide F is the precursor of a variety of fungal prenylated alkaloids with biological activity, including fumitremorgins A, B and C and tryprostatin B.

Based on the structural information of acetylaszonalenin isolated from Neosartorya fischeri, a putative biosynthetic gene cluster was identified in the genome sequence of this fungus by genomic mining. This cluster consists of three genes coding for a putative non-ribosomal peptide synthetase (AnaPS), a prenyltransferase (AnaPT), and an acetyltransferase (AnaAT). The coding sequences of anaPT and anaAT were cloned in pQE70 and pQE60, respectively, and overexpressed in Escherichia coli. The soluble His 6 fusion proteins were purified to near homogeneity and characterized biochemically. The structures of the enzymatic products were elucidated by NMR and mass spectroscopy analysis. AnaPT was found to catalyze the reverse prenylation of (

Verruculogen is a tremorgenic mycotoxin and contains an endoperoxide bond. In this study, we describe the cloning, overexpression and purification of a non-heme Fe(ii) and alpha-ketoglutarate-dependent dioxygenase FtmOx1 from Aspergillus fumigatus, which catalyses the conversion of fumitremorgin B to verruculogen by inserting an endoperoxide bond between two prenyl moieties. Incubation with (18)O(2)-enriched atmosphere demonstrated that both oxygen atoms of the endoperoxide bond are derived from one molecule of O(2). FtmOx1 is the first endoperoxide-forming non-heme Fe(ii) and alpha-ketoglutarate-dependent dioxygenase reported so far. A mechanism of FtmOx1-catalysed verruculogen formation is postulated and discussed.