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Biomedical subjects

A Zeeck

Publications and source records attributed to A Zeeck.

At least 55 records · Page 3Linked to original sources
PubMed1994

Influence of increased dissolved oxygen concentration on productivity and selectivity in cultures of a colabomycin-producing strain of Streptomyces griseoflavus.

The influence of enhanced O2 concentration on growth and formation of secondary metabolites by Streptomyces griseoflavus (strain Tü 2880) was investigated in a stirred tank and in an air-lift fermentor. At a partial pressure of O2 Po2 = 1880 mbar the growth was lowered by 50% compared to Po2 = 210 mbar, whilst substrate consumption and O2 uptake rate increased markedly. Production of the colabomycin complex reached maximum values at Po2 = 630 mbar. A similar increase of secondary metabolite formation was obtained when glycerol or acetate were fed at Po2 = 220 mbar. The portion of the derivate colabomycin A in the product mixture rose from 43% at Po2 = 210 mbar to 73% at Po2 = 1260 mbar. Since dissolved O2 concentration has a significant influence on productivity and selectivity it may be used to regulate aerobic fermentation processes.

Alkenes↗
PubMed1994

Secondary metabolites by chemical screening, 26.1 7-O-beta-D-galactosyl-brefeldin A via transglycosylation with Penicillium brefeldianum.

A lactose-containing fermentation medium initiated the formation of 7-O-beta-D-galactosyl-brefeldin A [1] in the brefeldin A-producing organism, Penicillium brefeldianum. The detection, isolation, and physicochemical properties of 1, which has been produced by biological derivatization via transglycosylation, are described. Compound 1 is the first glycosylated brefeldin A derivative to have been prepared.

Animals↗
PubMed1994

Biosynthetic capacities of actinomycetes. 2. Juglomycin Z, a new naphthoquinone antibiotic from Streptomyces tendae.

A new juglomycin-type antibiotic was identified by a HPLC-diode array screening technique in the culture filtrate of Streptomyces tendae Tü 901/8c. Juglomycin Z (1) differs from all other known juglomycin compounds by an additional methyl group in position 3 of the naphthoquinone ring system. Juglomycin Z is antibiotically active against Gram-positive and Gram-negative bacteria and against yeasts.

Anti-Bacterial Agents↗
PubMed1993

Purification and characterization of a pyranose oxidase from the basidiomycete Peniophora gigantea and chemical analyses of its reaction products.

A pyranose oxidase was isolated from mycelium extracts of the basidiomycete Peniophora gigantea. This enzyme was purified 104-fold to apparent homogeneity with a yield of about 75% by steps involving fractionated ammonium sulphate precipitation, chromatography on DEAE-Sephacel, Sephacryl S 300, S Sepharose and Q Sepharose. The native pyranose oxidase has a relative molecular mass (M(r)) of 322,800 +/- 18,300 as determined on the basis of its Stokes' radius (rs = 6.2 nm) and sedimentation coefficient (S20,w = 10.6), dynamic light-scattering experiments, gradient-gel electrophoresis and cross-linking studies. SDS/PAGE resulted in one single polypeptide band of M(r) 76,000 indicating that the enzyme consists of four subunits of identical size. The pyranose oxidase was shown to be an extremely stable glycoprotein with an isoelectric point of pH 5.3. It contains covalently bound FAD with an estimated stoichiometry of 3.6 molecules FAD/molecule enzyme. Pyranose oxidase was active with the substrates D-glucose, D-xylose, L-sorbose, D-galactose, methyl beta-D-glucoside, maltose and D-fucose. Regioselective oxidation of D-glucose, L-sorbose and D-xylose to 2-keto-D-glucose, 5-keto-D-fructose and 2-keto-D-xylose, was demonstrated by identifying the reaction products by mass spectroscopy 13C-NMR spectroscopy and 1H-NMR spectroscopy after purification and derivatization. The pH optimum of the pyranose oxidase was in the range pH 6.0-6.5 in 0.1 M potassium phosphate, and its activation energy (delta H degree) for the conversion of D-glucose was 34.6 kJ/mol. The reactions with the sugars exhibited Michaelis-Menten kinetics, and the Km values determined for D-glucose, L-sorbose, D-xylose and oxygen were 1.1 mM, 50.0 mM, 29.4 mM and 0.65 mM, respectively. The activity of pyranose oxidase was only slightly affected by chelating reagents, thiol reagents, reducing reagents and bivalent cations each at 1 mM.

Basidiomycota↗
PubMed1993

Inhibitory effect of modified bafilomycins and concanamycins on P- and V-type adenosinetriphosphatases.

Various ATPases have been tested for their sensitivity to naturally occurring unusual macrolides and their chemically modified derivatives, which are structurally related to bafilomycin A1 (1), the first specific inhibitor of vacuolar ATPases. The structure-activity study showed that in general the concanamycins, 18-membered macrolides, are better and more specific inhibitors than the bafilomycins of this class of membrane-bound ATPases. The additional carbohydrate residue is not responsible for the improved activity. The importance of an intact hemiketal ring, which is part of an intramolecular hydrogen-bonding network, and the effects of the size of the macrolactone ring are discussed. The structurally related elaiophylin (13), a C2-symmetric macrodiolide antibiotic, proved to be inactive on vacuolar ATPases but still retained its inhibitory effect on P-type ATPases.

ATP Synthetase Complexes↗
PubMed1992

Metabolic products of microorganisms. 261. Obscurolides, a novel class of phosphodiesterase inhibitors from streptomyces. I. Production, isolation, structural elucidation and biological activity of obscurolides A1 to A4.

A novel class of butyrolactones, named obscurolides, was isolated from the culture filtrate of Streptomyces viridochromogenes by chemical screening methods. The structural elucidation of the obscurolides A1 to A4 (1 approximately 4) is described. The carboxy group of the 4-aminobenzoic acid moiety of obscurolide A1 (1) is reduced in the other compounds. The isolated natural products have been proved to be diastereomeric mixtures by a partial racemization at C-7 which belongs to an allylic alcohol system. The obscurolides showed a weak inhibitory activity against calcium/calmodulin-dependent and independent phosphodiesterases from bovine.

4-Butyrolactone↗
PubMed1992

Secondary metabolites by chemical screening. 8. Decarestrictines, a new family of inhibitors of cholesterol biosynthesis from Penicillium. I. Strain description, fermentation, isolation and properties.

A family of new 10-membered lactones was detected by chemical screening. Taxonomic studies and fermentation conditions of the producing organisms, which belong to the species Penicillium simplicissimum and Penicillium corylophilum, are presented. The isolation as well as physico-chemical data of the new compounds named decarestrictines A to D are reported. In vitro testing using the HEP-G2 cell assay showed the decarestrictines to be inhibitors of cholesterol biosynthesis, which could be confirmed in vivo. In addition to the decarestrictines from P. corylophilum epoxyagroclavine-I (1) was isolated.

Animals↗
PubMed1992

Secondary metabolites by chemical screening. 9. Decarestrictines, a new family of inhibitors of cholesterol biosynthesis from Penicillium. II. Structure elucidation of the decarestrictines A to D.

The structures of the novel 10-membered lactones, named decarestrictines A1/A2 (1/2), B (3), C1/C2 (5/6) and D (7), are presented. The structures of these secondary metabolites, isolated from different Penicillium species, were established by spectroscopic analysis and confirmed by X-ray analysis of 7 and a derivative of 3 leading to the stereochemical information. The decarestrictines vary in the oxygenation pattern between C-3 and C-7 and show structural similarities to known lactones from other fungi.

Anticholesteremic Agents↗
PubMed1990

Structure-activity relationships of elloramycin and tetracenomycin C.

The structure-activity relationships of the anthracycline-related antibiotics of the tetracenomycin C/elloramycin-type were investigated by derivatization of elloramycin (1) and elloramycinone (2). During hydrolysis experiments a unique transglycosylation reaction was discovered, converting elloramycin (1) into isoelloramycin (10) by treatment with anhydrous trifluoroacetic acid. Following the proposed structure-activity relationship concept, 8-O-methylelloramycinone (14) was synthesized from elloramycinone (2), and was shown to be the most active derivative according to the proliferation inhibition assay against murine L1210 leukemia cells.

Animals↗