Identification of volatiles from six marine strains.

The volatiles emitted from six marine species of the genus were investigated by GC-MS. Besides several known compounds including dimethyl trisulfide and -methyl methanethiosulfonate, the sulfur-containing compounds ethyl ()-3-(methylsulfanyl)acrylate and 2-(methyldisulfanyl)benzothiazole were identified and their structures were verified by synthesis. Feeding experiments with [-H]methionine, [-C]methionine and [S]-3-(dimethylsulfonio)propanoate (DMSP) resulted in the high incorporation into dimethyl trisulfide and -methyl methanethiosulfonate, and revealed the origin of the methylsulfanyl group of 2-(methyldisulfanyl)benzothiazole from methionine or DMSP, while the biosynthetic origin of the benzothiazol-2-ylsulfanyl portion could not be traced.

Mechanistic divergence between (4,7)-germacra-(1(10),5)-dien-11-ol synthases from and .

The main product of DpTPS9 from the social amoeba Dictyostelium purpureum was identified as (4S,7R)-germacra-(1(10)E,5E)-dien-11-ol that is also known as an intermediate of bacterial geosmin synthase, but the experimentally verified cyclisation mechanisms differ. Together with the low sequence identity this points to convergent evolution. The functionality of selected residues in DpTPS9 was investigated via site-directed mutagenesis experiments.

Characterization of Micromonocyclol Synthase from the Marine Actinomycete .

As a member of a large phylogenetic clade of enzymes in , a terpene synthase from is functionally characterized to produce micromonocyclol. This diterpene alcohol features a rare 15-membered ring, which prevented elucidation of the only stereocenter by labeling experiments. This problem was addressed by chemical transformation into bicyclic brominated derivatives, whose rigidified skeletons allowed for a stereochemical assignment.

Characterisation of three terpene synthases for β-barbatene, β-araneosene and nephthenol from social amoebae.

The products of three terpene synthases from two social amoebae, Dictyostelium discoideum and Dictyostelium purpureum, were identified, showing sesquiterpene synthase activity for one and diterpene synthase activity for the other two enzymes. Site-directed mutagenesis experiments revealed the importance of a newly identfied highly conserved residue for catalytic activity. For one of the enzyme products, β-araneosene, a bromonium ion induced transannular cyclisation was investigated, yielding the first brominated derivatives of this diterpene.

Mechanistic Studies on Trichoacorenol Synthase from Amycolatopsis benzoatilytica.

Isotopic labeling experiments performed with a newly identified bacterial trichoacorenol synthase established a 1,5-hydride shift occurring in the cyclization mechanism. During EI-MS analysis, major fragments of the sesquiterpenoid were shown to arise via cryptic hydrogen movements. Therefore, the interpretation of earlier results regarding the cyclization mechanism obtained by feeding experiments in Trichoderma is revised.

A Family of Related Fungal and Bacterial Di- and Sesterterpenes: Studies on Fusaterpenol and Variediene.

The absolute configuration of fusaterpenol (GJ1012E) has been revised by an enantioselective deuteration strategy. A bifunctional enzyme with a terpene synthase and a prenyltransferase domain from Aspergillus brasiliensis was characterised as variediene synthase, and the absolute configuration of its product was elucidated. The uniform absolute configurations of these and structurally related di- and sesterterpenes together with a common stereochemical course for the geminal methyl groups of GGPP unravel a similar conformational fold of the substrate in the active sites of the terpene synthases.

Terpene Synthase Genes Originated from Bacteria through Horizontal Gene Transfer Contribute to Terpenoid Diversity in Fungi.

Fungi are successful eukaryotes of wide distribution. They are known as rich producers of secondary metabolites, especially terpenoids, which are important for fungi-environment interactions. Horizontal gene transfer (HGT) is an important mechanism contributing to genetic innovation of fungi.

Mechanistic investigations on multiproduct β-himachalene synthase from .

A bacterial terpene synthase from was characterised as a multiproduct β-himachalene synthase. In vitro studies showed not only a high promiscuity with respect to its numerous sesquiterpene products, including the structurally demanding terpenes longicyclene, longifolene and α-longipinene, but also to its substrates, as additional activity was observed with geranyl- and geranylgeranyl diphosphate. In-depth mechanistic investigations using isotopically labelled precursors regarding the stereochemical course of both 1,11-cyclisation and 1,3-hydride shift furnished a detailed catalytic model suggesting the molecular basis of the observed low product selectivity.

Diterpene Biosynthesis in Actinomycetes: Studies on Cattleyene Synthase and Phomopsene Synthase.

Three diterpene synthases from actinomycetes have been studied. The first enzyme from Streptomyces cattleya produced the novel compound cattleyene. The other two enzymes from Nocardia testacea and Nocardia rhamnosiphila were identified as phomopsene synthases.

Stereochemical investigations on the biosynthesis of achiral ()-γ-bisabolene in .

A newly identified bacterial ()-γ-bisabolene synthase was used for investigating the cyclisation mechanism of the sesquiterpene. Since the stereoinformation of both chiral putative intermediates, nerolidyl diphosphate (NPP) and the bisabolyl cation, is lost during formation of the achiral product, the intriguing question of their absolute configurations was addressed by incubating both enantiomers of NPP with the recombinant enzyme, which resolved in an exclusive cyclisation of ()-NPP, while ()-NPP that is non-natural to the ()-γ-bisabolene synthase was specifically converted into ()-β-farnesene. A hypothetical enzyme mechanistic model that explains these observations is presented.

Addressing the Chemistry of Germacrene A by Isotope Labeling Experiments.

Despite the central role of germacrene A in sesquiterpene biosynthesis and its widespread occurrence in nature, its complete NMR characterization is still pending. This problem was solved through enzymatic preparation of germacrene A isotopomers that allowed for a full signal assignment to all three conformers. The obtained materials gave insights into the stereochemical course of the Cope rearrangement to β-elemene and uncovered the Cope rearrangement as a new EI-MS fragmentation reaction.

Volatiles from the hypoxylaceous fungi and .

The volatiles emitted by the ascomycetes and (Hypoxylaceae, Xylariales) were collected by use of a closed-loop stripping apparatus (CLSA) and analysed by GC-MS. The main compound class of both species were polysubstituted benzene derivatives. Their structures could only be unambiguously determined by comparison to all isomers with different substitution patterns.

A Branched Diterpene Cascade: The Mechanism of Spinodiene Synthase from Saccharopolyspora spinosa.

A diterpene synthase from Saccharopolyspora spinosa was found to convert geranylgeranyl diphosphate into the new natural products spinodiene A and B, accompanied by 2,7,18-dolabellatriene. The structures and the formation mechanism of the enzyme products were investigated by extensive isotopic labelling experiments, which revealed an unusual branched isomerisation mechanism towards the neutral intermediate 2,7,18-dolabellatriene. A Diels-Alder reaction was used to convert the main diterpene product with its rare conjugated diene moiety into formal sesterterpene alcohols.

A Clade II-D Fungal Chimeric Diterpene Synthase from Colletotrichum gloeosporioides Produces Dolasta-1(15),8-diene.

Based on a terpenoid overproduction platform in yeast for genome mining, a chimeric diterpene synthase from the endophytic fungus Colletotrichum gloeosporioides ES026 was characterized as the (5R,12R,14S)-dolasta-1(15),8-diene synthase. The absolute configuration was independently verified through the use of enantioselectively deuterated terpene precursors, which unequivocally established the predicted C1-III-IV cyclization mode for this first characterized clade II-D enzyme. Extensive isotopic labeling experiments and isolation of the intermediate (1R)-δ-araneosene supported the proposed cyclization mechanism.

Sesquiterpene Cyclisations Catalysed inside the Resorcinarene Capsule and Application in the Short Synthesis of Isolongifolene and Isolongifolenone.

Terpenes constitute the largest class of natural products and serve as an important source for medicinal treatments. Despite constant progress in chemical synthesis, the construction of complex polycyclic sesqui- and diterpene scaffolds remains challenging. Natural cyclase enzymes, however, are able to form the whole variety of terpene structures from just a handful of linear precursors.

Acyl-group specificity of AHL synthases involved in quorum-sensing in group bacteria.

-Acylhomoserine lactones (AHLs) are important bacterial messengers, mediating different bacterial traits by quorum sensing in a cell-density dependent manner. AHLs are also produced by many bacteria of the marine group, which constitutes a large group within the marine microbiome. Often, specific mixtures of AHLs differing in chain length and oxidation status are produced by bacteria, but how the biosynthetic enzymes, LuxI homologs, are selecting the correct acyl precursors is largely unknown.

Two Bacterial Diterpene Synthases from Allokutzneria albata Produce Bonnadiene, Phomopsene, and Allokutznerene.

Two diterpene synthases from Allokutzneria albata were studied for their products, resulting in the identification of the new compound bonnadiene from the first enzyme. Although phylogenetically unrelated to fungal phomopsene synthase, the second enzyme produced a mixture of phomopsene and a biosynthetically linked new compound, allokutznerene, as well as spiroviolene. Both enzymes were subjected to in-depth mechanistic studies involving isotopic labelling experiments, metal-cofactor variation, and site-directed mutagenesis.

An Isotopic Labelling Strategy to Study Cytochrome P450 Oxidations of Terpenes.

The cytochrome P450 monooxygenase CYP267B1 from Sorangium cellulosum was applied for the enzymatic oxidation of the sesquiterpene alcohols T-muurolol and isodauc-8-en-11-ol. Various isotopically labelled geranyl and farnesyl diphosphates were used for product identification from micro-scale reactions, for the determination of the absolute configurations of unknown compounds, to follow the stereochemical course of a cytochrome P450-catalysed hydroxylation step, and to investigate kinetic isotope effects. Overall, this study demonstrates that isotopically labelled terpene precursors are highly useful to follow cytochrome P450 dependent oxidations of terpenes.

From lignin to nylon: Cascaded chemical and biochemical conversion using metabolically engineered Pseudomonas putida.

Cis,cis-muconic acid (MA) is a chemical that is recognized for its industrial value and is synthetically accessible from aromatic compounds. This feature provides the attractive possibility of producing MA from mixtures of aromatics found in depolymerized lignin, the most underutilized lignocellulosic biopolymer. Based on the metabolic pathway, the catechol (1,2-dihydroxybenzene) node is the central element of this type of production process: (i) all upper catabolic pathways of aromatics converge at catechol as the central intermediate, (ii) catechol itself is frequently generated during lignin pre-processing, and (iii) catechol is directly converted to the target product MA by catechol 1,2-dioxygenase.

Two Diterpene Synthases for Spiroalbatene and Cembrene A from Allokutzneria albata.

Two bacterial diterpene synthases from the actinomycete Allokutzneria albata were investigated, resulting in the identification of the structurally unprecedented compound spiroalbatene from the first and cembrene A from the second enzyme. Both enzymes were thoroughly investigated in terms of their mechanisms by isotope labeling experiments, site-directed mutagenesis, and variation of the metal cofactors and pH value. For spiroalbatene synthase, the pH- and Mn -dependent formation of the side product thunbergol was observed, which is biosynthetically linked to spiroalbatene.

Spata-13,17-diene Synthase-An Enzyme with Sesqui-, Di-, and Sesterterpene Synthase Activity from Streptomyces xinghaiensis.

A terpene synthase from the marine bacterium Streptomyces xinghaiensis has been characterised, including a full structure elucidation of its products from various substrates and an in-depth investigation of the enzyme mechanism by isotope labelling experiments, metal cofactor variations, and mutation experiments. The results revealed an interesting dependency of Mn catalysis on the presence of Asp-217, a residue that is occupied by a highly conserved Glu in most other bacterial terpene synthases.

18-Hydroxydolabella-3,7-diene synthase - a diterpene synthase from .

The product obtained in vitro from a diterpene synthase encoded in the genome of the bacterium , an enzyme previously reported to have germacrene A synthase activity during heterologous expression in , was identified by extensive NMR-spectroscopic methods as 18-hydroxydolabella-3,7-diene. The absolute configuration of this diterpene alcohol and the stereochemical course of the terpene synthase reaction were addressed by isotopic labelling experiments. Heterologous expression of the diterpene synthase in resulted in the production of 18-hydroxydolabella-3,7-diene also in planta, while the results from the heterologous expression in were shown to be reproducible, revealing that the expression of one and the same terpene synthase in different heterologous hosts may yield different terpene products.

Characterisation of the l-Cystine β-Lyase PatB from Phaeobacter inhibens: An Enzyme Involved in the Biosynthesis of the Marine Antibiotic Tropodithietic Acid.

The l-cystine β-lyase from Phaeobacter inhibens is involved in the biosynthesis of the sulfur-containing antibiotic tropodithietic acid. The recombinant enzyme was obtained by heterologous expression in Escherichia coli and biochemically characterised by unambiguous chemical identification of the products formed from the substrate l-cystine, investigation of the substrate spectrum, determination of the enzyme kinetics, sequence alignment with closely related homologues and site-directed mutagenesis to identify a highly conserved lysine residue that is critical for functionality. PatB from P.

Mechanisms of the Diterpene Cyclases β-Pinacene Synthase from Dictyostelium discoideum and Hydropyrene Synthase from Streptomyces clavuligerus.

Two diterpene cyclases, one from the social amoeba Dictyostelium discoideum and the other from the bacterium Streptomyces clavuligerus, with products containing a Z-configured double bond between the original C2 and C3 of geranylgeranyl diphosphate, were extensively investigated for their mechanisms through isotopic labelling experiments. The participation of geranyllinalyl diphosphate, in analogy to the role of linalyl and nerolidyl diphosphate for mono- and sesquiterpene biosynthesis, as an intermediate towards diterpenes with a Z-configured C2=C3 double bond is discussed.

Mechanistic Characterization of Two Chimeric Sesterterpene Synthases from Penicillium.

The products of two bifunctional fungal sesterterpene synthases (StTPS), with prenyl transferase (PT) and terpene synthase (TPS) domains from Penicillium, were structurally characterized and their mechanisms studied in detail by labeling experiments. A phylogenetic analysis of the TPS domains of the new and previously characterized enzymes revealed six distinct clades. Enzymes from the same clade catalyze a common initial cyclization step, which suggests the potential for structural predictions from amino acid sequences.