Geschmack ist vorhersagbar: Mit FlavorMiner. FlavorMiner heißt das Tool, das IPB-Chemiker und Partner aus Kolumbien jüngst entwickelt haben. Das Programm kann, basierend auf maschinellem Lernen (KI), anhand der…
Seit Februar 2021 bietet Wolfgang Brandt, ehemaliger Leiter der Arbeitsgruppe Computerchemie am IPB, sein Citizen Science-Projekt zur Pilzbestimmung an. Dafür hat er in regelmäßigen Abständen öffentliche Vorträge zur Vielfalt…
Prasad, A.; Breithaupt, C.; Nguyen, D.-A.; Lilie, H.; Ziegler, J.; Stubbs, M. T.;Mechanism of chorismate dehydratase MqnA, the first enzyme of the futalosine pathway, proceeds via substrate-assisted catalysisJ. Biol. Chem.298102601(2022)DOI: 10.1016/j.jbc.2022.102601
MqnA, the only chorismate dehydratase known so far, catalyzes the initial step in the biosynthesis of menaquinone via the futalosine pathway. Details of the MqnA reaction mechanism remain unclear. Here, we present crystal structures of Streptomyces coelicolor MqnA and its active site mutants in complex with chorismate and the product 3-enolpyruvyl-benzoate, produced during heterologous expression in Escherichia coli. Together with activity studies, our data are in line with dehydration proceeding via substrate assisted catalysis, with the enol pyruvyl group of chorismate acting as catalytic base. Surprisingly, structures of the mutant Asn17Asp with copurified ligand suggest that the enzyme converts to a hydrolase by serendipitous positioning of the carboxyl group. All complex structures presented here exhibit a closed Venus flytrap fold, with the enzyme exploiting the characteristic ligand binding properties of the fold for specific substrate binding and catalysis. The conformational rearrangements that facilitate complete burial of substrate/product, with accompanying topological changes to the enzyme surface, could foster substrate channeling within the biosynthetic pathway.
Publikation
Chalo, D. M.; Kakudidi, E.; Origa-Oryem, H.; Namukobe, J.; Franke, K.; Yenesew, A.; Wessjohann, L. A.;Chemical constituents of the roots of Ormocarpum sennoides subsp. zanzibaricumBiochem. Syst. Ecol.93104142(2020)DOI: 10.1016/j.bse.2020.104142
Phytochemical investigation of the roots of O. sennoides subsp. zanzibaricum Brenan & J.B. Gillett resulted in the isolation of three biflavonoids (trime-chamaejasmin, (+)- chamaejasmin, (+)-liquiritigeninyl-(I-3,II-3)-naringenin), one bi-4-phenyldihydrocoumarin (diphysin), one isoflavan (glabridin), one triterpenoid (3-O-acetyloleanoic acid) and a phytosterol (β-sitosterol). Compounds were identified by detailed MS, 1D and 2D NMR spectroscopic analyses. Their absolute configurations were elucidated based on ECD spectra. The previously undescribed trime-chamaejasmin represents a bis-epi-chamaejasmenin C diastereomer. The chemophenetic significance is discussed in detail. The results contribute to the phytochemical characterization of the genus Ormocarpum and suggest a close chemophenetic relationship with other genera within the subfamily Papilionoideae. Furthermore, this report provides baseline data for comparing the two infraspecific taxa of O. sennoides (Willd.) DC.
Publikation
Tchatchouang Noulala, C. G.; Fotso, G. W.; Rennert, R.; Lenta, B. N.; Sewald, N.; Arnold, N.; Happi, E. N.; Ngadjui, B. T.;Mesomeric form of quaternary indoloquinazoline alkaloid and other constituents from the Cameroonian Rutaceae Araliopsis soyauxii Engl.Biochem. Syst. Ecol.91104050(2020)DOI: 10.1016/j.bse.2020.104050
A mesomeric form of quaternary indoloquinazoline alkaloid, soyauxinium chloride (1) was obtained through the chemical investigation of stem bark and roots of Araliopsis soyauxii Engl. [syn. Vepris soyauxii (Engl.) Mziray] (Rutaceae) together with fifteen known compounds, including three furoquinoline alkaloids, three 2-quinolones, two limonoids, two triterpenes, two steroids, a coumarin, an acridone alkaloid, and a flavonoid glycoside. Their structures were established by comprehensive spectroscopic and spectrometric analyses (1D and 2D NMR, ESI-HR-MS) and by comparison with previously reported data. 13C NMR data of araliopsinine are also reported here for the first time. The isolated compounds were screened in vitro for their effects on the viability of two different human cancer cell lines, namely prostate PC-3 adenocarcinoma cells and colorectal HT-29 adenocarcinoma cells. However, none of the tested compounds exhibited strong anti-proliferative or cytotoxic activities, to either prostate PC-3 cells or colon HT-29 cells. At 100 μM, the furoquinoline maculine showed a slightly increased anti-proliferative effect, however, exclusively on HT-29 cells. The chemotaxonomic significance of the isolated compounds has also been discussed.
Publikation
Matern, A.; Böttcher, C.; Eschen-Lippold, L.; Westermann, B.; Smolka, U.; Döll, S.; Trempel, F.; Aryal, B.; Scheel, D.; Geisler, M.; Rosahl, S.;A substrate of the ABC transporter PEN3 stimulates bacterial flagellin (flg22)-induced callose deposition in Arabidopsis thalianaJ. Biol. Chem.2946857-6870(2019)DOI: 10.1074/jbc.RA119.007676
Nonhost resistance of Arabidopsis thaliana against Phytophthora infestans, a filamentous eukaryotic microbe and the causal agent of potato late blight, is based on a multilayered defense system. Arabidopsis thaliana controls pathogen entry through the penetration-resistance genes PEN2 and PEN3, encoding an atypical myrosinase and an ABC transporter, respectively, required for synthesis and export of unknown indole compounds. To identify pathogen-elicited leaf surface metabolites and further unravel nonhost resistance in Arabidopsis, we performed untargeted metabolite profiling by incubating a P. infestans zoospore suspension on leaves of WT or pen3 mutant Arabidopsis plants. Among the plant-secreted metabolites, 4-methoxyindol-3-yl-methanol and S-(4-methoxy-indol-3-yl-methyl) cysteine were detected in spore suspensions recollected from WT plants, but at reduced levels from the pen3 mutant plants. In both whole-cell and microsome-based assays, 4-methoxyindol-3-yl-methanol was transported in a PEN3-dependent manner, suggesting that this compound is a PEN3 substrate. The syntheses of both compounds were dependent on functional PEN2 and phytochelatin synthase 1. None of these compounds inhibited mycelial growth of P. infestans in vitro. Of note, exogenous application of 4-methoxyindol-3-yl methanol slightly elevated cytosolic Ca2+ levels and enhanced callose deposition in hydathodes of seedlings treated with a bacterial pathogen-associated molecular pattern (PAMP), flagellin (flg22). Loss of flg22-induced callose deposition in leaves of pen3 seedlings was partially reverted by the addition of 4-methoxyindol-3-yl methanol. In conclusion, we have identified a specific indole compound that is a substrate for PEN3 and contributes to the plant defense response against microbial pathogens.