Rainer-B. Volk

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Culture medium extracts obtained from 115 culture media of 35 different microalgae species were screened for the presence of algicidal compounds, in particular for compounds which are cytotoxic to Arthrospira (Spirulina) laxissima. In agar plate diffusion tests and in a test system combining thin layer chromatography (TLC) with the use of an aqueous(More)
The isolation, identification and quantification of exometabolites from culture media of the cyanobacterium Nostoc insulare are described. Besides the known exometabolite 4,4′-dihydroxybiphenyl (I), two more compounds, the β-carboline 9H-pyrido(3,4-b)indole (norharmane, II) and N,N′-(4,5-dimethyl-1,2-phenylene)bis-acetamide (III), were discovered.(More)
GTP cyclohydrolase II catalyzes the first committed step in the biosynthesis of riboflavin. The gene coding for this enzyme in Escherichia coli has been cloned by marker rescue. Sequencing indicated an open reading frame of 588 bp coding for a 21.8-kDa peptide of 196 amino acids. The gene was mapped to a position at 28.2 min on the E. coli chromosome and is(More)
Screening of a Xenopus laevis oocyte cDNA library with a rat basic fibroblast growth factor (bFGF) cDNA led to the isolation of a 1.35 kb sequence containing exon III of the bFGF gene. Reverse complementary listing of this sequence revealed a polyadenylated transcript with an open reading frame coding for an unknown protein of mol. wt 24,292 daltons. The(More)
Changes in the content of exometabolites excreted by the cyanobacterium Nostoc insulare during batch cultivation were determined. During linear growth, only the non-toxic compound N,N′-(4,5-dimethyl-1,2-phenylene)-bis-acetamide was detectable in appreciable quantities in the medium, whereas during stationary growth the antimicrobial and cytotoxic(More)
The structural investigation of an extracellular polysaccharide released during photoautotrophic growth by the cyanobacterium Nostoc insulare is reported. After 60 days of cultivation, an average yield of purified, desalted, and freeze-dried released polysaccharide (RPS) of 0.9 g L−1 medium was obtained. The apparent hydrodynamic volume, determined for RPS,(More)
3,4-Dihydroxy-2-butanone 4-phosphate is biosynthesized from ribulose 5-phosphate and serves as the biosynthetic precursor for the xylene ring of riboflavin. The gene coding for 3,4-dihydroxy-2-butanone 4-phosphate synthase of Escherichia coli has been cloned and sequenced. The gene codes for a protein of 217 amino acid residues with a calculated molecular(More)
The riboflavin precursor, L-3,4-dihydroxy-2-butanone 4-phosphate, is formed from D-ribulose 5-phosphate by a single 24-kDa enzyme. Studies with various specifically 13C-labeled D-ribulose 5-phosphates as substrate showed that the carbon atoms 1-3 of the enzyme product correspond to carbon atoms 1-3 of the substrate, whereas C-4 of the product stems from C-5(More)
The formation of the riboflavin precursor, 6,7-dimethyl-8-ribityllumazine, from 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione requires a phosphorylated 4-carbon intermediate which has been designated as Compound X (Neuberger, G., and Bacher, A. (1985) Biochem. Biophys. Res. Commun. 127, 175-181). The enzyme catalyzing the formation of Compound X has(More)
The lumazine synthase/riboflavin synthase complex of Bacillus subtilis consists of an icosahedral capsid of 60 beta subunits surrounding a core of 3 alpha subunits. The beta subunits catalyze the condensation of 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione with (3S)-3,4-dihydroxy-2-butanone under formation of 6,7-dimethyl-8-ribityllumazine. This(More)