Unser 10. Leibniz Plant Biochemistry Symposium am 7. und 8. Mai war ein großer Erfolg. Thematisch ging es in diesem Jahr um neue Methoden und Forschungsansätze der Naturstoffchemie. Die exzellenten Vorträge über Wirkstoffe…
Omanische Heilpflanze im Fokus der Phytochemie IPB-Wissenschaftler und Partner aus Dhofar haben jüngst die omanische Heilpflanze Terminalia dhofarica unter die phytochemische Lupe genommen. Die Pflanze ist reich an…
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…
Wils, C. R.; Brandt, W.; Manke, K.; Vogt, T.;A single amino acid determines position specificity of an Arabidopsis thaliana CCoAOMT-like O-methyltransferaseFEBS Lett.587683-689(2013)DOI: 10.1016/j.febslet.2013.01.040
Caffeoyl‐coenzyme A O‐methyltransferase (CCoAOMT)‐like proteins from plants display a conserved position specificity towards the meta‐position of aromatic vicinal dihydroxy groups, consistent with the methylation pattern observed in vivo. A CCoAOMT‐like enzyme identified from Arabidopsis thaliana encoded by the gene At4g26220 shows a strong preference for methylating the para position of flavanones and dihydroflavonols, whereas flavones and flavonols are methylated in the meta‐position. Sequence alignments and homology modelling identified several unique amino acids compared to motifs of other CCoAOMT‐like enzymes. Mutation of a single glycine, G46 towards a tyrosine was sufficient for a reversal of the unusual para‐ back to meta‐O‐methylation of flavanones and dihydroflavonols.
Publikation
Haack, M.; Löwinger, M.; Lippmann, D.; Kipp, A.; Pagnotta, E.; Iori, R.; Monien, B. H.; Glatt, H.; Brauer, M. N.; Wessjohann, L. A.; Brigelius-Flohé, R.;Breakdown products of neoglucobrassicin inhibit activation of Nrf2 target genes mediated by myrosinase-derived glucoraphanin hydrolysis productsBiol. Chem.3911281-1293(2010)DOI: 10.1515/bc.2010.134
Glucosinolates (GLSs) present in Brassica vegetables serve as precursors for biologically active metabolites, which are released by myrosinase and induce phase 2 enzymes via the activation of Nrf2. Thus, GLSs are generally considered beneficial. The pattern of GLSs in plants is various, and contents of individual GLSs change with growth phase and culture conditions. Whereas some GLSs, for example, glucoraphanin (GRA), the precursor of sulforaphane (SFN), are intensively studied, functions of others such as the indole GLS neoglucobrassicin (nGBS) are rather unknown as are functions of combinations thereof. We therefore investigated myrosinase-treated GRA, nGBS and synthetic SFN for their ability to induce NAD(P)H:quinone oxidoreductase 1 (NQO1) as typical phase 2 enzyme, and glutathione peroxidase 2 (GPx2) as novel Nrf2 target in HepG2 cells. Breakdown products of nGBS potently inhibit both GRA-mediated stimulation of NQO1 enzyme and Gpx2 promoter activity. Inhibition of promoter activity depends on the presence of an intact xenobiotic responsive element (XRE) and is also observed with benzo[a]pyrene, a typical ligand of the aryl hydrocarbon receptor (AhR), suggesting that suppressive effects of nGBS are mediated via AhR/XRE pathway. Thus, the AhR/XRE pathway can negatively interfere with the Nrf2/ARE pathway which has consequences for dietary recommendations and, therefore, needs further investigation.
Publikation
Lukačin, R.; Matern, U.; Hehmann, M.; Specker, S.; Vogt, T.;Corrigendum to “Cations modulate the substrate specificity of bifunctional class I O-methyltransferase from Ammi majus” [FEBS Lett. 577 (2004) 367-370]FEBS Lett.583855-855(2009)DOI: 10.1016/j.febslet.2009.01.050
Putrescine N ‐methyltransferase (PMT) catalyses S ‐adenosylmethionine (SAM)‐dependent methylation of putrescine in tropane alkaloid biosynthesis. PMT presumably evolved from the ubiquitous spermidine synthase (SPDS). SPDS protein structure suggested that only few amino acid exchanges in the active site were necessary to achieve PMT activity. Protein modelling, mutagenesis, and chimeric protein construction were applied to trace back evolution of PMT activity from SPDS. Ten amino acid exchanges in Datura stramonium SPDS dismissed the hypothesis of facile generation of PMT activity in existing SPDS proteins. Chimeric PMT and SPDS enzymes were active and indicated the necessity for a different putrescine binding site when PMT developed.