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Bioorganic Chemistry
Biochemistry of Plant Interactions
Cell and Metabolic Biology
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Publications - Cell and Metabolic Biology
Publications
Precise annotation of time and spatial distribution of enzymes involved in plant secondary metabolism by gel electrophoresis are usually difficult due to their low abundance. Therefore, effective methods to enrich these enzymes are required to correlate available transcript and metabolite data with the actual presence of active enzymes in wild-type and mutant plants or to monitor variations of these enzymes under various types of biotic and abiotic stress conditions. S-Adenosyl-L-methionine-dependent O-methyltransferases play important roles in the modification of natural products such as phenylpropanoids or alkaloids. In plants they occur as small superfamilies with defined roles for each of its members in different organs and tissues. We explored the use of S-adenosyl-L-homocysteine as a selectivity function in affinity-based protein profiling supported by capture compound mass spectrometry. Due to their high affinity to this ligand it was possible to identify developmental changes of flower-specific patterns of plant natural product O-methyltransferases and corroborate the absence of individual O-methyltransferases in the corresponding Arabidopsis knockout lines. Developmental changes in the OMT pattern were correlated with transcript data obtained by qPCR.
Publications
De-oiled rapeseed is a rich source of proteins and phenolic compounds. The phenolic compounds, namely sinapic acid derivatives (SAD), could occur as free sinapic acid, esterified (as sinapine, the choline ester of sinapic acid) and decarboxylated (as canolol) forms. Rapeseed protein preparations containing very low phenolic compounds have been the focus of our ongoing research. A precipitated rapeseed protein isolate is investigated for SAD such as sinapine, sinapoyl glucose, canolol using HPLC–DAD and LC–MS. Profile of the phenolic compounds of de-oiled rapeseed, press cakes and the precipitated protein isolate are compared. HPLC–DAD analysis indicated SAD; particularly sinapine is the main phenolic compound of all the substrates. The protein derivation process did not remarkably alter the profile of the investigated protein isolate.
Publications
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Publications
In our studies on tyrosinase-catalyzed tyrosine hydroxylation, possibly involved in betalain biosynthesis, we have evaluated different assays for the detection and quantification of the enzymatic product Dopa with respect to sensitivity, simplicity, and suitability for automatization. A tyrosinase assay including reversed-phase high-performance liquid chromatography with isocratic elution and fluorescence detection has been developed (native fluorescence of Dopa; excitation at 281 nm, emission at 314 nm). This improved assay was sensitive (detection limit: 2 pmol Dopa) and showed a wide linear range of Dopa detection (10 pmol–20 nmol Dopa). The method proved to be suitable for high-performance liquid chromatography with an autosampler and has been applied for measuring tyrosinase activity of cell cultures and different tissues ofPortulaca grandiflora.
This page was last modified on 27 Jan 2025 .
