Search

Juvenile hormone (JH) plays a pivotal role in almost every aspect of insect development and reproduction. The chemical structure of the JH in heteropteran species has long remained elusive until methyl (2R,3S,10R)-2,3;10,11-bisepoxyfarnesoate, commonly named as juvenile hormone III skipped bisepoxide (JHSB3), was isolated from Plautia stali (Hemiptera: Heteroptera: Pentatomidae). Recently, several groups reported the presence of JHSB3 in other heteropteran species. However, most of the studies paid no attention to the determination of the relative and absolute structure of the JH. In this study, we investigated the JH of the cabbage bug Eurydema rugosa (Hemiptera: Heteroptera: Pentatomidae), known as a pest for wild and cultivated crucifers. JHSB3 was detected in the hexane extract from the corpus allatum (CA) product using a chiral ultraperformance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) which can inform the absolute stereochemistry of the JH. Its stereoisomers were not detected. Topical application of the synthetic JHSB3 to the last instar nymphs inhibited their metamorphosis and induced nymphal-type colouration of the dorsal abdomen in a dose-dependent manner. Additionally, the topical application of JHSB3 effectively terminated summer and winter diapauses in females. These results indicate that the JH of E. rugosa is JHSB3. Although individuals in summer and winter diapauses are physiologically distinct in E. rugosa, the results suggest that the physiological differences between these diapauses are based, not on the responsiveness to JH, but on the processes governing activation of the CA or on its upstream cascades.

Natural products containing an aziridine ring, such as mitomycin C and azinomycin B, exhibit antitumor activities by alkylating DNA via their aziridine rings; however, the biosynthetic mechanisms underlying the formation of these rings have not yet been elucidated. We herein investigated the biosynthesis of vazabitide A, the structure of which is similar to that of azinomycin B, and demonstrated that Vzb10/11, with no similarities to known enzymes, catalyzed the formation of the aziridine ring via sulfate elimination. To elucidate the detailed reaction mechanism, crystallization of Vzb10/11 and the homologous enzyme, AziU3/U2, in the biosynthesis of azinomycin B was attempted, and the structure of AziU3/U2, which had a new protein fold overall, was successfully determined. The structural analysis revealed that these enzymes adjusted the dihedral angle between the amino group and the adjacent sulfate group of the substrate to almost 180° and enhanced the nucleophilicity of the C6-amino group temporarily, facilitating the S

The C-H alkenylation of N-acetylcarbazoles proceeds smoothly at the C1-position in the presence of a cationic Cp*Rh(III) catalyst to produce 1-alkenylcarbazoles. The use of a cationic CpERh(III) catalyst enables further alkenylation to give 1,8-dialkenylcarbazoles. The direct alkenylation procedure in combination with the ready removal of the acetyl directing group provides a straightforward synthetic pathway to 1- and/or 8-alkenyl-N-H-carbazole derivatives. One of 1-alkenyl-N-H-carbazoles obtained by the present C-H alkenylation/deacetylation exhibits solvatochromism.

The mevalonate pathway is an upstream terpenoid biosynthetic route of terpenoids for providing the two five-carbon units, dimethylallyl diphosphate, and isopentenyl diphosphate. Recently, trans-anhydromevalonate-5-phosphate (tAHMP) was isolated as a new biosynthetic intermediate of the archaeal mevalonate pathway. In this study, we would like to report the first synthesis of tAHMP and its enzymatic transformation using one of the key enzymes, mevalonate-5-phosphate dehydratase from a hyperthermophilic archaeon, Aeropyrum pernix. Starting from methyl tetrolate, a Cu-catalyzed allylation provided an E-trisubstituted olefin in a stereoselective manner. The resulting E-olefin was transformed to tAHMP by cleavage of the olefin and phosphorylation. The structure of the synthetic tAHMP was unambiguously determined by NOESY analysis.

Terpene synthase (TS) from Bacillus alcalophilus (BalTS) is the only Class IB TS for which a 3D structure has been elucidated. Recently, geranyl-β-phellandrene, a novel cyclic diterpene, was identified as a product of BalTS in addition to the acyclic β-springene. In the present study, we have provided insight into the mechanism of geranyl-β-phellandrene formation. Deuterium labeling experiments revealed that the compound is produced via a 1,3-hydride shift. In addition, nonenzymatic reactions using divalent metal ions were performed. The enzyme is essential for the geranyl-β-phellandrene formation. Furthermore, BalTS variants targeting tyrosine residues enhanced the yield of geranyl-β-phellandrene and the proportion of the compound of the total products. It was suggested that the expansion of the active site space may allow the conformation of the intermediates necessary for cyclization. The present study describes the first Class IB TSs to successfully alter product profiles while retaining high enzyme activity.

Some enzymes annotated as squalene synthase catalyze the prenylation of carbazole-3,4-quinone-containing substrates in bacterial secondary metabolism. Their reaction mechanisms remain unclear because of their low sequence similarity to well-characterized aromatic substrate prenyltransferases (PTs). We determined the crystal structures of the carbazole PTs, and these revealed that the overall structure is well superposed on those of squalene synthases. In contrast, the stacking interaction between the prenyl donor and acceptor substrates resembles those observed in aromatic substrate PTs. Structural and mutational analyses suggest that the Ile and Asp residues are essential for the hydrophobic and hydrophilic interactions with the carbazole-3,4-quinone moiety of the prenyl acceptor, respectively, and a deprotonation mechanism of an intermediary σ-complex involving a catalytic triad is proposed. Our results provide a structural basis for a new subclass of aromatic substrate PTs.

The mevalonate pathway is an upstream terpenoid biosynthetic route of terpenoids for providing the two five-carbon units, dimethylallyl diphosphate, and isopentenyl diphosphate. Recently

Most temperate multivoltine insects enter diapause, a hormonally controlled developmental suspension, in response to seasonal photoperiodic and/or thermal cues. Some insect species exhibit maternal regulation of diapause in which developmental trajectories of the offspring are determined by mothers in response to environmental cues that the mother received. Although maternally regulated diapause is common among insects, the maternal endocrinological mechanisms are largely veiled. To approach this issue, we used the jewel wasp Nasonia vitripennis, which produces non-diapause-destined offspring under long days and diapause-destined offspring under short days or low temperatures. Comparative transcriptomics of these wasps revealed possible involvement of the juvenile hormone (JH) biosynthetic cascade in maternal diapause regulation. The expression of juvenile hormone acid O-methyltransferase (jhamt) was typically downregulated in short-day wasps, and this was reflected by a reduction in haemolymph JH concentrations. RNAi targeted at jhamt reduced haemolymph JH concentration and induced wasps to produce diapause-destined offspring even under long days. In addition, topical application of JH suppressed the production of diapause-destined offspring under short days or low temperatures. These results indicate that diapause in N. vitripennis is determined by maternal jhamt expression and haemolymph JH concentration in response to day length. We therefore report a novel role for JH in insect seasonality.