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Biomedical subjects

Jürgen Schmidt

Publications and source records attributed to Jürgen Schmidt.

At least 19 recordsLinked to original sources
PubMed2007

A polyketide synthase of Plumbago indica that catalyzes the formation of hexaketide pyrones.

Plumbago indica L. contains naphthoquinones that are derived from six acetate units. To characterize the enzyme catalyzing the first step in the biosynthesis of these metabolites, a cDNA encoding a type III polyketide synthase (PKS) was isolated from roots of P. indica. The translated polypeptide shared 47-60% identical residues with PKSs from other plant species. Recombinant P. indica PKS expressed in Escherichia coli accepted acetyl-CoA as starter and carried out five decarboxylative condensations with malonyl coenzyme A (-CoA). The resulting hexaketide was not folded into a naphthalene derivative. Instead, an alpha-pyrone, 6-(2',4'-dihydroxy-6'-methylphenyl)-4-hydroxy-2-pyrone, was produced. In addition, formation of alpha-pyrones with linear keto side chains derived from three to six acetate units was observed. As phenylpyrones could not be detected in P. indica roots, we propose that the novel PKS is involved in the biosynthesis of naphthoquinones, and additional cofactors are probably required for the biosynthesis of these secondary metabolites in vivo.

Amino Acid Sequence↗
PubMed2006

Poppy alkaloid profiling by electrospray tandem mass spectrometry and electrospray FT-ICR mass spectrometry after [ring-13C6]-tyramine feeding.

Papaver alkaloids play a major role in medicine and pharmacy. In this study, [ring-(13)C(6)]-tyramine as a biogenetic precursor of these alkaloids was fed to Papaver somniferum seedlings. The alkaloid pattern was elucidated both by direct infusion high-resolution ESI-FT-ICR mass spectrometry and liquid chromatography/electrospray tandem mass spectrometry. Thus, based on this procedure, the structure of about 20 alkaloids displaying an incorporation of the labeled tyramine could be elucidated. These alkaloids belong to different classes, e.g. morphinan, benzylisoquinoline, protoberberine, benzo[c]phenanthridine, phthalide isoquinoline and protopine. The valuable information gained from the alkaloid profile demonstrates that the combination of these two spectrometric methods represents a powerful tool for evaluating biochemical pathways and facilitates the study of the flux of distant precursors into these natural products.

Alkaloids↗
PubMed2006

PCR diagnosis of infections with different species of Opisthorchiidae using a rapid clean-up procedure for stool samples and specific primers.

Infections with the opisthorchiid liver flukes Clonorchis sinensis, Opisthorchis viverrini, and Opisthorchis felineus cause serious health problems in endemic areas of Southeast Asia and countries of the former Soviet Union. Chronic infections--even with low worm burdens--may lead to the development of fatal cholangiocarcinoma and related symptoms. A more sensitive diagnosis is needed since the tiny eggs of the worms are often not seen in microscopic examinations of stool samples, especially in patients with low infections. This communication reports a rapid cleanup procedure for human stool samples, which enables reliable identification of DNA by polymerase chain reaction from few eggs of opisthorchiid flukes in fecal samples.

Animals↗
PubMed2006

Comparative transcript and alkaloid profiling in Papaver species identifies a short chain dehydrogenase/reductase involved in morphine biosynthesis.

Plants of the order Ranunculales, especially members of the species Papaver, accumulate a large variety of benzylisoquinoline alkaloids with about 2500 structures, but only the opium poppy (Papaver somniferum) and Papaver setigerum are able to produce the analgesic and narcotic morphine and the antitussive codeine. In this study, we investigated the molecular basis for this exceptional biosynthetic capability by comparison of alkaloid profiles with gene expression profiles between 16 different Papaver species. Out of 2000 expressed sequence tags obtained from P. somniferum, 69 show increased expression in morphinan alkaloid-containing species. One of these cDNAs, exhibiting an expression pattern very similar to previously isolated cDNAs coding for enzymes in benzylisoquinoline biosynthesis, showed the highest amino acid identity to reductases in menthol biosynthesis. After overexpression, the protein encoded by this cDNA reduced the keto group of salutaridine yielding salutaridinol, an intermediate in morphine biosynthesis. The stereoisomer 7-epi-salutaridinol was not formed. Based on its similarities to a previously purified protein from P. somniferum with respect to the high substrate specificity, molecular mass and kinetic data, the recombinant protein was identified as salutaridine reductase (SalR; EC 1.1.1.248). Unlike codeinone reductase, an enzyme acting later in the pathway that catalyses the reduction of a keto group and which belongs to the family of the aldo-keto reductases, the cDNA identified in this study as SalR belongs to the family of short chain dehydrogenases/reductases and is related to reductases in monoterpene metabolism.

Alkaloids↗
PubMed2006

Synthesis of N-(beta-D-glucopyranosyl) monoamides of dicarboxylic acids as potential inhibitors of glycogen phosphorylase.

O-peracetylated N-(beta-D-glucopyranosyl)imino trimethylphosphorane obtained in situ from 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl azide and PMe3 was reacted with saturated and unsaturated aliphatic and aromatic dicarboxylic acids, or their anhydrides, or monoesters to give the corresponding N-(beta-D-glucopyranosyl) monoamides of dicarboxylic acids or derivatives. The acetyl protecting groups were removed according to the Zemplén protocol to give a series of compounds which showed moderate inhibitory effects against rabbit muscle glycogen phosphorylase b. The best inhibitor was 3-(N-beta-D-glucopyranosyl-carbamoyl)propanoic acid (7) with Ki = 20 microM.

Amides↗
PubMed2006

Cassini dust measurements at Enceladus and implications for the origin of the E ring.

During Cassini's close flyby of Enceladus on 14 July 2005, the High Rate Detector of the Cosmic Dust Analyzer registered micron-sized dust particles enveloping this satellite. The dust impact rate peaked about 1 minute before the closest approach of the spacecraft to the moon. This asymmetric signature is consistent with a locally enhanced dust production in the south polar region of Enceladus. Other Cassini experiments revealed evidence for geophysical activities near Enceladus' south pole: a high surface temperature and a release of water gas. Production or release of dust particles related to these processes may provide the dominant source of Saturn's E ring.

Atmosphere↗
PubMed2006

Biotransformation of 1-naphthol by a strictly aquatic fungus.

The aquatic hyphomycete Heliscus lugdunensis belongs to a group of exclusively aquatic mitosporic fungi with an only scarcely explored potential to oxidatively attack xenobiotic compounds, and was used to study the biotransformation of the environmental pollutant metabolite 1-naphthol. H. lugdunensis metabolized approximately 74% of 1-naphthol within 5 days. The identification and quantification of degradation products using gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and high performance liquid chromatography revealed that approximately 12% of the parent compound was converted into 1-naphthylsulfate, 3% was transformed into 1-methoxy-naphthalene, and less than 1% was converted into 1,4-naphthoquinone. A further metabolite, most likely 4-hydroxy-1-naphthylsulfate, was also detected. In contrast to sulfate conjugate metabolites, no glucuronide and glucoside conjugates of 1-naphthol were found, and neither UDP-glucuronyltransferase nor UDP-glucosyltransferase present in H. lugdunensis showed activity towards 1-naphthol. These results support a role of fungi adapted to aquatic environments in affecting the environmental fate of pollutants in aquatic ecosystems.

Biotransformation↗
PubMed2006

Analysis of fungal cyclopentenone derivatives from Hygrophorus spp. by liquid chromatography/electrospray-tandem mass spectrometry.

Fruitbodies of the genus Hygrophorus (Basidiomycetes) contain a series of anti-biologically active compounds. These substances named hygrophorones possess a cyclopentenone skeleton. LC/ESI-MS/MS presents a valuable tool for the identification of such compounds. The mass spectral behaviour of typical selected members of this group under positive and negative ion electrospray conditions is discussed. Using the ESI collision-induced dissociation (CID) mass spectra of the [M + H]+ and [M - H]- ions, respectively, the compounds can be classified with respect to the substitution pattern at the cyclopentenone ring and the type of oxygenation at C-6 (hydroxy/acetoxy or oxo function) of the side chain. The elemental composition of the fragment ions was determined by ESI-QqTOF measurements. Thus, in case of the negative ion CID mass spectra an unusual loss of CO2 from the deprotonated molecular ions could be observed.

Agaricales↗
PubMed2006

Accumulation of apocarotenoids in mycorrhizal roots of Ornithogalum umbellatum.

Colonization of roots of Ornithogalum umbellatum by the arbuscular mycorrhizal fungus Glomus intraradices induced the accumulation of different types of apocarotenoids. In addition to the mycorrhiza-specific occurrence of cyclohexenone derivatives and the "yellow pigment" described earlier, free mycorradicin and numerous mycorradicin derivatives were detected in a complex apocarotenoid mixture for the first time. From the accumulation pattern of the mycorradicin derivatives their possible integration into the continuously accumulating "yellow pigment" is suggested. Structure analyses of the cyclohexenone derivatives by MS and NMR revealed that they are mono-, di- and branched triglycosides of blumenol C, 13-hydroxyblumenol C, and 13-nor-5-carboxy-blumenol C, some of which contain terminal rhamnose as sugar moiety.

Carotenoids↗
PubMed2006

[The satisfaction of relatives with service delivery of nursing homes for the elderly. Development of the screening-questionnaire ZUF-A-7].

PURPOSE: To enable the measurement of satisfaction with the service delivery of residential homes, a practicable and statistical proven screening-test was supposed to educe. In order to identify critical quality-related situations a specific cut-off should be allocated. METHODS: Based on literature research a questionnaire was developed and responded by 3581 relatives of residents of 45 nursing homes for the elderly. The questionnaire was analysed and compressed based on scale, item and factor analysis. For validation, demographic variables and separate quality-ratings were available. Finally a ROC analysis was performed to recognize specificity and sensitivity of possible cut-offs. RESULTS: The Angehörigen-Screening-Fragebogen (relatives-screening-questionnaire) ZUF-A-7 was generated consisting of seven items. The scale is reliable (Cronbach's Alpha). Like other satisfaction measurements it displays a skew distribution. Middle size up to large correlations with the quality-ratings exists but there were no relevant coherences to the demographic variables. The ROC analysis suggested a critical cut-off of 21 (range = 7-28).

Aged↗
PubMed2006

Desiccation of the resurrection plant Craterostigma plantagineum induces dynamic changes in protein phosphorylation.

Reversible phosphorylation of proteins is an important mechanism by which organisms regulate their reactions to external stimuli. To investigate the involvement of phosphorylation during acquisition of desiccation tolerance, we have analysed dehydration-induced protein phosphorylation in the desiccation tolerant resurrection plant Craterostigma plantagineum. Several dehydration-induced proteins were shown to be transiently phosphorylated during a dehydration and rehydration (RH) cycle. Two abundantly expressed phosphoproteins are the dehydration- and abscisic acid (ABA)-responsive protein CDeT11-24 and the group 2 late embryogenesis abundant (LEA) protein CDeT6-19. Although both proteins accumulate in leaves and roots with similar kinetics in response to dehydration, their phosphorylation patterns differ. Several phosphorylation sites were identified on the CDeT11-24 protein using liquid chromatography-tandem mass spectrometry (LCMS/MS). The coincidence of phosphorylation sites with predicted coiled-coil regions leads to the hypothesis that CDeT11-24 phosphorylations influence the stability of coiled-coil interactions with itself and possibly other proteins.

Amino Acid Motifs↗
PubMed2005

Flavonols and an indole alkaloid skeleton bearing identical acylated glycosidic groups from yellow petals of Papaver nudicaule.

From yellow petals of Iceland poppy, besides the known flavonoid gossypitrin, seven kaempferol derivatives were isolated. In addition to kaempferol 3-O-beta-sophoroside and kaempferol 3-O-beta-sophoroside-7-O-beta-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.

Alkaloids↗
PubMed2005

A reference map of the Arabidopsis thaliana mature pollen proteome.

The male gametophyte (or pollen) plays an obligatory role during sexual reproduction of higher plants. The extremely reduced complexity of this organ renders pollen a valuable experimental system for studying fundamental aspects of plant biology such as cell fate determination, cell-cell interactions, cell polarity, and tip-growth. Here, we present the first reference map of the mature pollen proteome of the dicotyledonous model plant species, Arabidopsis thaliana. Based on two-dimensional gel electrophoresis, matrix-assisted laser desorption/ionization time-of-flight, and electrospray quadrupole time-of-flight mass spectrometry, we reproducibly identified 121 different proteins in 145 individual spots. The presence, subcellular localization, and functional classification of the identified proteins are discussed in relation to the pollen transcriptome and the full protein complement encoded by the nuclear Arabidopsis genome.

Arabidopsis↗
PubMed2005

A stilbene synthase gene (SbSTS1) is involved in host and nonhost defense responses in sorghum.

A chalcone synthase (CHS)-like gene, SbCHS8, with high expressed sequence tag abundance in a pathogen-induced cDNA library, was identified previously in sorghum (Sorghum bicolor). Genomic Southern analysis revealed that SbCHS8 represents a single-copy gene. SbCHS8 expression was induced in sorghum mesocotyls following inoculation with Cochliobolus heterotrophus and Colletotrichum sublineolum, corresponding to nonhost and host defense responses, respectively. However, the induction was delayed by approximately 24 h when compared to the expression of at least one of the other SbCHS genes. In addition, SbCHS8 expression was not induced by light and did not occur in a tissue-specific manner. SbCHS8, together with SbCHS2, was overexpressed in transgenic Arabidopsis (Arabidopsis thaliana) tt4 (transparent testa) mutants defective in CHS activities. SbCHS2 rescued the ability of these mutants to accumulate flavonoids in seed coats and seedlings. In contrast, SbCHS8 failed to complement the mutation, suggesting that the encoded enzyme does not function as a CHS. To elucidate their biochemical functions, recombinant proteins were assayed with different phenylpropanoid-Coenzyme A esters. Flavanones and stilbenes were detected in the reaction products of SbCHS2 and SbCHS8, respectively. Taken together, our data demonstrated that SbCHS2 encodes a typical CHS that synthesizes naringenin chalcone, which is necessary for the formation of different flavonoid metabolites. On the other hand, SbCHS8, now retermed SbSTS1, encodes an enzyme with stilbene synthase activity, suggesting that sorghum accumulates stilbene-derived defense metabolites in addition to the well-characterized 3-deoxyanthocyanidin phytoalexins.

Acyltransferases↗
PubMed2005

Extract of the seeds of the plant Vitex agnus castus proven to be highly efficacious as a repellent against ticks, fleas, mosquitoes and biting flies.

About 70 plant extracts were tested for their ability to repel the attacks of blood-sucking arthropods. It was found that a CO2 extract of the seeds of the Mediterranean plant Vitex agnus castus (monk's pepper) can be used as a spray to keep away especially Ixodes ricinus and Rhipicephalus sanguineus ticks from animals and humans for at least 6 h. In addition mosquitoes, biting flies and fleas are also repelled for about 6 h.

Animals↗
PubMed2005

Formation of a complex pattern of sinapate esters in Brassica napus seeds, catalyzed by enzymes of a serine carboxypeptidase-like acyltransferase family?

Members of the Brassicaceae accumulate complex patterns of sinapate esters, as shown in this communication with seeds of oilseed rape (Brassica napus). Fifteen seed constituents were isolated and identified by a combination of high-field NMR spectroscopy and high resolution electrospray ionisation mass spectrometry. These include glucose, gentiobiose and kaempferol glycoside esters as well as sinapine (sinapoylcholine), sinapoylmalate and an unusual cyclic spermidine amide. One of the glucose esters (1,6-di-O-sinapoylglucose), two gentiobiose esters (1-O-caffeoylgentiobiose and 1,2,6'-tri-O-sinapoylgentiobiose) and two kaempferol conjugates [4'-(6-O-sinapoylglucoside)-3,7-di-O-glucoside and 3-O-sophoroside-7-O-(2-O-sinapoylglucoside)] seem to be new plant products. Serine carboxypeptidase-like (SCPL) acyltransferases catalyze the formation of sinapine and sinapoylmalate accepting 1-O-beta-acetal esters (1-O-beta-glucose esters) as acyl donors. To address the question whether the formation of other components of the complex pattern of the sinapate esters in B. napus seeds is catalyzed via 1-O-sinapoyl-beta-glucose, we performed a seed-specific dsRNAi-based suppression of the sinapate glucosyltransferase gene (BnSGT1) expression. In seeds of BnSGT1-suppressing plants the amount of sinapoylglucose decreased below the HPLC detection limit resulting in turn in the disappearance or marked decrease of all the other sinapate esters, indicating that formation of the complex pattern of these esters in B. napus seeds is dependent on sinapoylglucose. This gives rise to the assumption that enzymes of an SCPL acyltransferase family catalyze the appropriate transfer reactions to synthesize the accumulating esters.

Acyltransferases↗