Discovery of dimethylsulfoxonium propionate lyases - a missing enzyme relevant to the global sulfur cycle.

Six dimethylsulfoniopropionate (DMSP) lyases have been shown to cleave the marine sulfur metabolite dimethylsulfoxonium propionate (DMSOP) into DMSO and acrylate. This discovery characterises a missing enzyme relevant to the global sulfur cycle.

Labelling studies in the biosynthesis of polyketides and non-ribosomal peptides.

Covering: 2015 to 2022In this review, we discuss the recent advances in the use of isotopically labelled compounds to investigate the biosynthesis of polyketides, non-ribosomally synthesised peptides, and their hybrids. Also, we highlight the use of isotopes in the elucidation of their structures and investigation of enzyme mechanisms. The biosynthetic pathways of selected examples are presented in detail to reveal the principles of the discussed labelling experiments.

Mechanistic Characterisation and Engineering of Sesterviolene Synthase from Streptomyces violens.

The sesterviolene synthase from Streptomyces violens was identified and represents the second known sesterterpene synthase from bacteria. Isotopic labelling experiments in conjunction with DFT calculations were performed that provided detailed insight into its complex cyclisation mechanism. Enzyme engineering through site-directed mutagenesis gave access to a high-yielding enzyme variant that provided six additional minor products and the main product in sufficient quantities to study its chemistry.

The substrate scope of dehydratases in antibiotic biosynthesis and their application in kinetic resolutions.

Nine dehydratases involved in the biosynthesis of secondary metabolites in addition to FabZ from fatty acid biosynthesis were investigated for their substrate scope using a panel of -acetylcysteamine (SNAC) thioesters. The best performing enzyme BorDH2 was applied in kinetic resolutions.

Origin of the 3-methylglutaryl moiety in caprazamycin biosynthesis.

Background: Caprazamycins are liponucleoside antibiotics showing bioactivity against Gram-positive bacteria including clinically relevant Mycobacterium tuberculosis by targeting the bacterial MraY-translocase. Their chemical structure contains a unique 3-methylglutaryl moiety which they only share with the closely related liposidomycins. Although the biosynthesis of caprazamycin is understood to some extent, the origin of 3-methylglutaryl-CoA for caprazamycin biosynthesis remains elusive.

Talaropeptins A and B, Tripeptides with an --Cinnamoyl Moiety from the Marine-Derived Fungus CX11.

We report the discovery of talaropeptins A () and B (), tripeptides with an unusual 5/6/5 heterocyclic scaffold and an --cinnamoyl moiety, which were identified from the marine-derived fungus CX11. A bioinformatic analysis of the genome of CX11 and gene inactivation revealed that the biosynthesis of talaropeptins involves a nonribosomal peptide synthase gene cluster. Their chemical structures were elucidated using a combination of 1D and 2D NMR spectroscopy and mass spectrometry.

Neuronal Ganglioside and Glycosphingolipid (GSL) Metabolism and Disease : Cascades of Secondary Metabolic Errors Can Generate Complex Pathologies (in LSDs).

Glycosphingolipids (GSLs) are a diverse group of membrane components occurring mainly on the surfaces of mammalian cells. They and their metabolites have a role in intercellular communication, serving as versatile biochemical signals (Kaltner et al, Biochem J 476(18):2623-2655, 2019) and in many cellular pathways. Anionic GSLs, the sialic acid containing gangliosides (GGs), are essential constituents of neuronal cell surfaces, whereas anionic sulfatides are key components of myelin and myelin forming oligodendrocytes.

Structural Disorder as the Origin of Optical Properties and Spectral Dynamics in Squaraine Nano-Aggregates.

In contrast to regular J- and H-aggregates, thin film squaraine aggregates usually have broad absorption spectra containing both J-and H-like features, which are favorable for organic photovoltaics. Despite being successfully applied in organic photovoltaics for years, a clear interpretation of these optical properties by relating them to specific excited states and an underlying aggregate structure has not been made. In this work, by static and transient absorption spectroscopy on aggregated -butyl anilino squaraines, we provide evidence that both the red- and blue-shifted peaks can be explained by assuming an ensemble of aggregates with intermolecular dipole-dipole resonance interactions and structural disorder deriving from the four different nearest neighbor alignments─in sharp contrast to previous association of the peaks with intermolecular charge-transfer interactions.

Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes.

Squaraines are prototypical quadrupolar charge-transfer chromophores that have recently attracted much attention as building blocks for solution-processed photovoltaics, fluorescent probes with large two-photon absorption cross sections, and aggregates with large circular dichroism. Their optical properties are often rationalized in terms of phenomenological essential state models, considering the coupling of two zwitterionic excited states to a neutral ground state. As a result, optical transitions to the lowest S1 excited state are one-photon allowed, whereas the next higher S2 state can only be accessed by two-photon transitions.

Diterpene Biosynthesis from Geranylgeranyl Diphosphate Analogues with Changed Reactivities Expands Skeletal Diversity.

Two analogues of the diterpene precursor geranylgeranyl diphosphate with shifted double bonds, named iso-GGPP I and iso-GGPP II, were enzymatically converted with twelve diterpene synthases from bacteria, fungi and protists. The changed reactivity in the substrate analogues resulted in the formation of 28 new diterpenes, many of which exhibit novel skeletons.

Extracellular hemin is a reverse use-dependent gating modifier of cardiac voltage-gated Na channels.

Heme (Fe-protoporphyrin IX) is a well-known protein prosthetic group; however, heme and hemin (Fe-protoporphyrin IX) are also increasingly viewed as signaling molecules. Among the signaling targets are numerous ion channels, with intracellular-facing heme-binding sites modulated by heme and hemin in the sub-µM range. Much less is known about extracellular hemin, which is expected to be more abundant, in particular after hemolytic insults.

Crystal Structure Based Mutagenesis of Cattleyene Synthase Leads to the Generation of Rearranged Polycyclic Diterpenes.

The crystal structures of cattleyene synthase (apo-CyS), and CyS complexed with geranylgeranyl pyrophosphate (GGPP) were solved. The CyS variant exhibited an increased production of cattleyene and other diterpenes with diverse skeletons. Its structure showed a widened active site cavity explaining the relaxed selectivity.

Chemistry and Analysis of Organic Compounds in Dinosaurs.

This review provides an overview of organic compounds detected in non-avian dinosaur fossils to date. This was enabled by the development of sensitive analytical techniques. Non-destructive methods and procedures restricted to the sample surface, e.

Engineering fungal terpene biosynthesis.

Covering: 2015 to 2022Fungal terpenoids are of large structural diversity and often exhibit interesting biological activities. Recent work has focused on two main aspects: (1) the discovery and understanding of unknown biosynthetic genes and pathways, and (2) the usage of already known biosynthetic genes in the construction of high yielding production strains. Both aspects will be covered in this review article that aims to summarise the most important work of the past few years.

High Versatility of IPP and DMAPP Methyltransferases Enables Synthesis of C , C and C Terpenoid Building Blocks.

The natural substance class of terpenoids covers an extremely wide range of different structures, although their building block repertoire is limited to the C compounds DMAPP and IPP. This study aims at the characterization of methyltransferases (MTases) that modify these terpene precursors and the demonstration of their suitability for biotechnological purposes. All seven enzymes tested accepted IPP as substrate and altogether five C compounds and six C compounds were formed within the reactions.

A non-natural biosynthesis pathway toward 2-methylisoborneol.

The biosynthesis of 2-methylisoborneol was reconstituted by elongation of dimethylallyl diphosphate (DMAPP) with ()- and ()-2-methylisopentenyl diphosphate (2-Me-IPP) using farnesyl diphosphate synthase (FPPS), followed by terpene cyclisation. The stereochemical course of the FPPS reaction was studied in detail using stereoselectively deuterated 2-Me-IPP isotopomers.

Plasmon-Enhanced Exciton Delocalization in Squaraine-Type Molecular Aggregates.

Enlarging exciton coherence lengths in molecular aggregates is critical for enhancing the collective optical and transport properties of molecular thin film nanostructures or devices. We demonstrate that the exciton coherence length of squaraine aggregates can be increased from 10 to 24 molecular units at room temperature when preparing the aggregated thin film on a metallic rather than a dielectric substrate. Two-dimensional electronic spectroscopy measurements reveal a much lower degree of inhomogeneous line broadening for aggregates on a gold film, pointing to a reduced disorder.

Enzymatic Synthesis of Variediene Analogs.

Five analogs of dimethylallyl diphosphate (DMAPP) with additional or shifted Me groups were converted with isopentenyl diphosphate (IPP) and the fungal variediene synthase from Aspergillus brasiliensis (AbVS). These enzymatic reactions resulted in the formation of several new terpene analogs that were isolated and structurally characterised by NMR spectroscopy. Several DMAPP analogs showed a changed reactivity giving access to compounds with unusual skeletons.

Mechanism of the Bifunctional Multiple Product Sesterterpene Synthase AcAS from Aspergillus calidoustus.

The multiproduct chimeric sesterterpene synthase AcAS from Aspergillus calidoustus yielded spirocyclic calidoustene, which exhibits a novel skeleton, besides five known sesterterpenes. The complex cyclisation mechanism to all six compounds was investigated by isotopic labelling experiments in combination with DFT calculations. Chemically synthesised 8-hydroxyfarnesyl diphosphate was converted with isopentenyl diphosphate and AcAS into four oxygenated sesterterpenoids that structurally resemble cytochrome P450 oxidation products of the sesterterpene hydrocarbons.

Isotopic Labeling Experiments Solve the Hedycaryol Problem.

Hedycaryol is a widespread sesquiterpene alcohol and important biosynthetic intermediate toward eudesmols and guaiols. A full NMR assignment for this compound has been hampered because of the unique molecular mechanics of its conformers in complex mixtures. This problem was solved through the enzymatic synthesis of isotopically labeled materials using a mutated plant and a bacterial enzyme for access to both enantiomers of hedycaryol, which also allowed us to follow the stereochemical course of its Cope rearrangement.

Stereochemical characterisation of the non-canonical α-humulene synthase from .

The non-canonical fungal α-humulene synthase was investigated through isotopic labelling experiments for its stereochemical course regarding inversion or retention at C-1, the face selectivity at C-11, and the stereoselectivity of the final deprotonation. A new and convenient desymmetrisation strategy was developed to enable a full stereochemical analysis of the catalysed steps to the achiral α-humulene product from stereoselectively labelled farnesyl diphosphate.

Using Terpene Synthase Plasticity in Catalysis: On the Enzymatic Conversion of Synthetic Farnesyl Diphosphate Analogues.

Four synthetic farnesyl diphosphate analogues were enzymatically converted with three bacterial sesquiterpene synthases, including β-himachalene synthase (HcS) and (Z)-γ-bisabolene synthase (BbS) from Cryptosporangium arvum, and germacrene A synthase (SmTS6) from Streptomyces mobaraensis. These enzyme reactions not only yielded several previously unknown compounds, showing that this approach opened the door to a new chemical space, but substrates with blocked or altered reactivities also gave interesting insights into the cyclisation mechanisms and the potential to catalyse reactions with different initial cyclisation modes.

Functional Switch and Ethyl Group Formation in the Bacterial Polytrichastrene Synthase from Chryseobacterium polytrichastri.

A reinvestigation of the linalool synthase from Chryseobacterium polytrichastri uncovered its diterpene synthase activity, yielding polytrichastrene A and polytrichastrol A with new skeletons, besides known wanju-2,5-diene and thunbergol. The enzyme mechanism was investigated by isotopic labeling experiments and DFT calculations to explain an unusual ethyl group formation. Rationally designed exchanges of active site residues showed major functional switches, resulting for I66F in the production of five more new compounds, including polytrichastrene B and polytrichastrol B, while A87T, A192V and the double exchange A87T, A192V gave a product shift towards wanju-2,5-diene.

The Mechanism of Dehydrating Bimodules in trans-Acyltransferase Polyketide Biosynthesis: A Showcase Study on Hepatoprotective Hangtaimycin.

A bioassay-guided fractionation led to the isolation of hangtaimycin (HTM) from Streptomyces spectabilis CCTCC M2017417 and the discovery of its hepatoprotective properties. Structure elucidation by NMR suggested the need for a structural revision. A putative HTM degradation product was also isolated and its structure was confirmed by total synthesis.

1,2- or 1,3-Hydride Shifts: What Controls Guaiane Biosynthesis?

A systematic computational study addressing the entire chemical space of guaianes in conjunction with an analysis of all known compounds shows that 1,3-hydride shifts are rare events in guaiane biosynthesis. As demonstrated here, 1,3-hydride shifts towards guaianes can only be realized for two stereochemically well defined out of numerous possible stereoisomeric skeletons. One example is given by the mechanism of guaia-4(15)-en-11-ol synthase from California poplar, an enzyme that yields guaianes with unusual stereochemical properties.