Formation of 3‑Orsellinoxypropanoic Acid in <i>Penicillum crustosum</i> is Catalyzed by a Bifunctional Nonreducing Polyketide Synthase

The heterologous expression of a nonreducing polyketide synthase gene oesA from Penicillium crustosum led to the identification of orsellinoylpropanoic acid (1). Domain deletion and recombination proved that OesA catalyzes not only the formation of orsellinic acid but also its transfer to 3-hydroxypropanoic acid. Both ACP domains contribute independently and complementarily to the product formation. Feeding experiments provided evidence that only the orsellinyl residue is derived from acetate

Regiospecific Benzylation of Tryptophan and Derivatives Catalyzed by a Fungal Dimethylallyl Transferase

A big challenge in organic synthesis is to reach a high regioselectivity. Enzymes catalyze usually highly regiospecific reactions and can function as ideal biocatalysts for such purposes. Some secondary metabolite enzymes can even use distinctly different unnatural substrates and expand therefore their potential usage in chemoenzymatic synthesis. We report here the acceptance of benzyl diphosphate as an alkyl donor by the fungal dimethylallyl transferase FgaPT2 and the regiospecific enzymatic benzylation of tryptophan and several analogues

Two Cytochrome P450 Enzymes from <i>Streptomyces</i> sp. NRRL S‑1868 Catalyze Distinct Dimerization of Tryptophan-Containing Cyclodipeptides

Heterologous expression in Streptomyces coelicolor and in vitro enzyme characterization proved that two P450 enzymes, AspB and NasB, from Streptomyces sp. NRRL S-1868 catalyze two new dimerization patterns of tryptophan-containing cyclodipeptides. Structure elucidation of the metabolites revealed an N1–C7′ dimer of two cWP molecules as the predominant product of AspB and C3–C7′ connected cWP with cWA as that of NasB

Breaking Cyclic Dipeptide Prenyltransferase Regioselectivity by Unnatural Alkyl Donors

The behavior of five cyclic dipeptide prenyltransferases, responsible for C2-regular, C2-reverse, or C3-reverse prenylation, was investigated in the presence of the unnatural alkyl donors monomethylallyl and 2-pentenyl diphosphate. Both substrates were well accepted by the tested enzymes. Interestingly, C2-reverse and C3-reverse monoalkylated derivatives were identified as enzyme products in all of the enzyme assays. These findings indicate their similar reaction characteristics in the presence of unnatural alkyl donors

Colletotriauxins A–D, New Plant Growth Inhibitors from the Phytopathogenic Fungus Colletotrichum gloeosporioides

Four undescribed plant growth inhibitory indole derivatives, colletotriauxins A–D (1–4), along with two known analogues indole-3-acetic acid (IAA) (5) and its amide indole-3-acetamide (6), were isolated from the phytopathogenic fungus Colletotrichum gloeosporioides NRRL 45420. Their structures were elucidated by NMR and MS analyses. 1 and 2 are rhamnosides of indole-3-ethanol (tryptophol) and its methylated derivative, respectively. In the structures of 3 and 4, the two terminal hydroxyl groups of hexitol and pentane-1,2,3,4,5-pentol are connected with indole-3-(2-methyl)-acetyl and acetyl moieties. Compounds 1–6 inhibit Lepidium sativum seedling growth. The inhibition activities of colletotriauxins for stem growth were even stronger than IAA, with compounds 3 and 4 as the most active ones. These results suggested that colletotriauxins could serve as potential candidates as herbicides

Expansion of Enzymatic Friedel–Crafts Alkylation on Indoles: Acceptance of Unnatural β‑Unsaturated Allyl Diphospates by Dimethylallyl-tryptophan Synthases

Prenyltransferases of the dimethylallyl-tryptophan synthase (DMATS) superfamily catalyze Friedel–Crafts alkylation with high flexibility for aromatic substrates, but the high specificity for dimethylallyl diphosphate (DMAPP) prohibits their application as biocatalysts. We demonstrate here that at least one methyl group in DMAPP can be deleted or shifted to the δ-position. For acceptance by some DMATS enzymes, however, a double bond must be situated at the β-position. Furthermore, the alkylation position of an analogue can differ from that of DMAPP

Design of α‑Keto Carboxylic Acid Dimers by Domain Recombination of Nonribosomal Peptide Synthetase (NRPS)-Like Enzymes

Nonribosomal peptide synthetase (NRPS)-like enzymes comprising A–T–TE architectures catalyze the dimerization of α-keto carboxylic acids leading to the formation of hydroxybenzoquinones or lactones. Domain change experiments with five enzymes revealed that A and A–T domains of phenyl or 4-hydroxyphenyl pyruvate-using enzymes can be effectively used by the TE domains of other enzymes. Even the A and A–T domains of an indolyl hydroxybenzoquinone synthase were successfully recombined with TE domains of a phenyl and a 4-hydroxyphenyl pyruvate-activating enzyme

Substrate Promiscuity of the Cyclic Dipeptide Prenyltransferases from <i>Aspergillus fumigatus</i>

This study reports that a series of tryptophan derivatives with modifications on the side chain or at the indole ring were accepted by two cyclic dipeptide prenyltransferases, CdpNPT and FtmPT1, and converted to prenylated derivatives. The structures of the enzymatic products were elucidated by NMR and MS analyses. In comparison to cyclic dipeptides, which were reversely prenylated by CdpNPT at N-1 and in a regular manner by FtmPT1 at C-2, respectively, tryptophan and its simple derivatives were prenylated reversely by both enzymes at N-1. These results demonstrated the substrate promiscuity of both enzymes

Coupling of <i>cyclo</i>-l‑Trp‑l‑Trp with Hypoxanthine Increases the Structure Diversity of Guanitrypmycins

The cyclo-l-Trp-l-Trp (cWW, 1) tailoring P450 GutD2774 from Streptomyces lavendulae was characterized by expression in Streptomyces coelicolor, precursor feeding and enzyme assays. GutD2774 catalyzes mainly the transfer of hypoxanthine to C2 and C3 of the indole ring of 1. cWW adducts with guanine were detected as minor products. An orthologous cluster was identified in Streptomyces xanthophaeus. These results expand the spectrum of cyclodipeptide derivatives by involvement of an additional nucleobase and identification of new coupling patterns

Friedel–Crafts Alkylation of Acylphloroglucinols Catalyzed by a Fungal Indole Prenyltransferase

Naturally occurring prenylated acylphloroglucinol derivatives are plant metabolites with diverse biological and pharmacological activities. Prenylation of acylphloroglucinols plays an important role in the formation of these intriguing natural products and is catalyzed in plants by membrane-bound enzymes. In this study, we demonstrate the prenylation of such compounds by a soluble fungal prenyltransferase AnaPT involved in the biosynthesis of prenylated indole alkaloids. The observed activities of AnaPT toward these substrates are much higher than that of a microsomal fraction containing an overproduced prenyltransferase from the plant hop