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Publications - Cell and Metabolic Biology

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Publications

Schliemann, W.; Schneider, B.; Wray, V.; Schmidt, J.; Nimtz, M.; Porzel, A.; Böhm, H.; Flavonols and an indole alkaloid skeleton bearing identical acylated glycosidic groups from yellow petals of Papaver nudicaule Phytochemistry 67, 191-201, (2006) DOI: 10.1016/j.phytochem.2005.11.002

From yellow petals of Iceland poppy, besides the known flavonoid gossypitrin, seven kaempferol derivatives were isolated. In addition to kaempferol 3-O-β-sophoroside and kaempferol 3-O-β-sophoroside-7-O-β-glucoside, known from other plants, the mono- and dimalonyl conjugates of the latter were identified by MS and NMR spectroscopy. Structure analyses of a set of co-occurring pigments, the nudicaulins, revealed that they have the identical acylated glycoside moieties attached to a pentacyclic indole alkaloid skeleton for which the structure of 19-(4-hydroxyphenyl)-10H-1,10-ethenochromeno[2,3-b]indole-6,8,18-triol was deduced from MS and NMR as well as chemical and chiroptical methods.
Publications

Eckermann, C.; Schröder, G.; Eckermann, S.; Strack, D.; Schmidt, J.; Schneider, B.; Schröder, J.; Stilbenecarboxylate biosynthesis: a new function in the family of chalcone synthase-related proteins Phytochemistry 62, 271-286, (2003) DOI: 10.1016/S0031-9422(02)00554-X

Chalcone (CHS), stilbene (STS) synthases, and related proteins are key enzymes in the biosynthesis of many secondary plant products. Precursor feeding studies and mechanistic rationalization suggest that stilbenecarboxylates might also be synthesized by plant type III polyketide synthases; however, the enzyme activity leading to retention of the carboxyl moiety in a stilbene backbone has not yet been demonstrated. Hydrangea macrophylla L. (Garden Hortensia) contains stilbenecarboxylates (hydrangeic acid and lunularic acid) that are derived from 4-coumaroyl and dihydro-4-coumaroyl starter residues, respectively. We used homology-based techniques to clone CHS-related sequences, and the enzyme functions were investigated with recombinant proteins. Sequences for two proteins were obtained. One was identified as CHS. The other shared 65–70% identity with CHSs and other family members. The purified recombinant protein had stilbenecarboxylate synthase (STCS) activity with dihydro-4-coumaroyl-CoA, but not with 4-coumaroyl-CoA or other substrates. We propose that the enzyme is involved in the biosynthesis of lunularic acid. It is the first example of a STS-type reaction that does not lose the terminal carboxyl group during the ring folding to the end product. Comparisons with CHS, STS, and a pyrone synthase showed that it is the only enzyme exerting a tight control over decarboxylation reactions. The protein contains unusual residues in positions highly conserved in other CHS-related proteins, and mutagenesis studies suggest that they are important for the structure or/and the catalytic activity. The formation of the natural products in vivo requires a reducing step, and we discuss the possibility that the absence of a reductase in the in vitro reactions may be responsible for the failure to obtain stilbenecarboxylates from substrates like 4-coumaroyl-CoA.Hydrangea macrophylla (Garden Hortensia) encodes a type III polyketide synthase synthesizing the stilbenecarboxylate backbone which is the basis for the biosynthesis of many secondary products in liverworts and in higher plants.
Publications

Opitz, S.; Schnitzler, J.-P.; Hause, B.; Schneider, B.; Histochemical analysis of phenylphenalenone-related compounds in Xiphidium caeruleum (Haemodoraceae) Planta 216, 881-889, (2003) DOI: 10.1007/s00425-002-0941-z

Phenylphenalenones represent a typical group of secondary metabolites of the Haemodoraceae. Some of these phenolic compounds show organ-specific distribution within the plant. However, detailed information on cellular localisation is still lacking. To this end, confocal laser-scanning microscopy, microspectral photometry and high-performance liquid chromatography were used to study the tissue localisation of phenylphenalenone-type compounds in Xiphidium caeruleum Aubl. From the autofluorescence potential of these compounds, specific distribution of allophanylglucosides and non-glucosidic compounds of the phenylphenalenone-type in distinct cells of the roots (apical meristem, cortex, cap, epidermis) and the shoot system was revealed. Fluorescence enhancement using "Naturstoff reagent A" (NA) indicated the occurrence of NA-positive natural products in the vacuoles of leaf epidermal cells. The present results provide new insights into the possible functions of phenylphenalenone-related compounds in the context of their localisation. Additionally, the advantages and limitations of the techniques are discussed.
Publications

Winter, J.; Schneider, B.; Meyenburg, S.; Strack, D.; Adam, G.; Monitoring brassinosteroid biosynthetic enzymes by fluorescent tagging and HPLC analysis of their substrates and products Phytochemistry 51, 237-242, (1999) DOI: 10.1016/S0031-9422(98)00760-2

Both the vicinal side chain hydroxyl groups and the 6-oxo function of brassinosteroids were modified by fluorescence tagging. Dansylaminophenylboronic acid was used as a derivatizing agent to form fluorescent esters of brassinosteroids containing a side-chain cis-diol structure. 6-Oxo type brassinosteroids were derivatized by means of dansylhydrazine. The modified brassinosteroids, as far as possible derivatized both at the diol and the oxo group, were separated by HPLC and the optimal emission wavelength was determined. By this approach almost all brassinosteroids, including biosynthetic precursors, were susceptible to highly sensitive analysis in the fmol range. This method has been verified as an analytical tool to determine brassinosteroids in cell culture extracts and to monitor brassinosteroid biosynthetic enzymes. 24-Epibrassinolide has been detected in tomato cell suspension cultures. Several steps of brassinosteroid biosynthesis, including the Baeyer–Villiger oxidation of 24-epicastasterone to give 24-epibrassinolide, were monitored in vitro with protein preparations of the same cell culture line.
Publications

Maier, W.; Schneider, B.; Strack, D.; Biosynthesis of sesquiterpenoid cyclohexenone derivatives in mycorrhizal barley roots proceeds via the glyceraldehyde 3-phosphate/pyruvate pathway Tetrahedron Lett. 39, 521-524, (1998) DOI: 10.1016/S0040-4039(97)10673-6

Incorporation of [1-13C]- and [U-13C6]glucose indicates that the biosynthesis of sesquiterpenoid cyclohexenone derivatives in mycorrhizal barley roots proceeds via the glyceraldehyde 3-phosphate/pyruvate non-mevalonate pathway.Incorporation of label from [1-13C]glucose (•) and [U-13C6]glucose ( − ) into the aglycon part (blumenol C) of blumenin indicates that in barley roots the arbuscular mycorrhizal fungus Glomus intraradices induces the glyceraldehyde 3-phosphate/pyruvate non-mevalonate pathway leading to sesquiterpenoid cyclohexenone derivatives.
Publications

Winter, J.; Schneider, B.; Strack, D.; Adam, G.; Role of a cytochrome P450-dependent monooxygenase in the hydroxylation of 24-epi-brassinolide Phytochemistry 45, 233-237, (1997) DOI: 10.1016/S0031-9422(96)00827-8

24-epi-Brassinolide, exogenously applied to cell suspension cultures of Lycopersicon esculentum is hydroxylated at C-25 and C-26, respectively, followed by glucosylation of the newly formed hydroxyl group. Treatment of the cell cultures with the specific cytochrome P450 inhibitors, clotrimazole and ketoconazole, resulted in a strong decrease of only the C-25 hydroxylation, whereas hydroxylation at C-26 was not affected. The common cytochrome P450 inducers, ethanol, MnCl2, phenobarbital, pregnenolone 16α-carbonitrile or clofibrate, did not induce hydroxylation activity at C-25 or at C-26. In addition, substrate analogues (22S,23S-homobrassinolide, 24-epi-castasterone, ecdysone, and 20-OH-ecdysone) were not accepted. Only application of 24-epi-brassinolide and brassinolide resulted in an increased activity of both the C-25- and C-26-hydroxylases. For further examination of the molecular level of this inducing effect, the influence of the protein biosynthesis inhibitor cycloheximide has been studied. Thus, increase of both hydroxylase activities is obviously based on gene expression by action of the substrates, 24-epi-brassinolide and brassinolide.
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