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H Zähner

Publications and source records attributed to H Zähner.

At least 19 recordsLinked to original sources
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

Metabolic products of microorganisms. 263. Nikkomycins SZ, SX, SoZ and SoX, new intermediates associated to the nikkomycin biosynthesis of Streptomyces tendae.

New intermediates associated with nikkomycin biosynthesis, called nikkomycins SZ, SX, SoZ and SoX, were isolated and characterized from the culture broth of Streptomyces tendae Tü 901/S 2566. They are analogues to octosyl acids, shunt metabolites of polyoxin biosynthesis. The decreasing amounts of nikkomycins SZ and SX, produced in the culture medium, shows a significant correlation to the increasing amounts of the biologically active nikkomycins Z and X, dependent on the increasing concentration of iron.

Aminoglycosides↗
PubMed1991

Structure-activity relationships of the nikkomycins.

The structure-activity relationships of different nikkomycins were studied to evaluate the structural requirements for a potent chitin synthase inhibitor. We investigated the transport of the nikkomycins via the peptide transport system of the yeast Yarrowia lipolytica and determined the kinetic parameters for nikkomycin Z uptake [Km = 24 microM, Vmax = 2.2 nmol min-1 (mg dry wt)-1]. We demonstrated that the beta-methyl group of the N-terminal amino acid of dipeptide nikkomycins protects the molecule against peptidase activity in crude cell-extracts of different fungi. Furthermore, the relationship between inhibition constants for chitin synthase, transport of the nikkomycins via the peptide transport system, susceptibility to degradation by cellular proteases and whole-cell activity of the nikkomycins are discussed.

Aminoglycosides↗
PubMed1991

Metabolic products of microorganisms. 258. Enzymatic bromination of nikkomycin Z.

Two brominated nikkomycins were produced by enzymatic halogenation of nikkomycin Z in the presence of a nonheme bromoperoxidase isolated from Streptomyces aureofaciens Tü 24. The monobrominated and dibrominated nikkomycin Z derivatives were substituted at the hydroxypyridyl moiety of the N-terminal amino acid of nikkomycin Z at position C-6"' (ZBr) or C-4"' and C-6"' (ZBr2). The brominated nikkomycin Z derivatives had a decreased affinity to chitin synthase of Coprinus cinereus as compared to nikkomycin Z and exhibited a low inhibitory activity towards various fungi and yeasts.

Aminoglycosides↗
PubMed1990

Staphyloferrin A: a structurally new siderophore from staphylococci.

Two ferric ion-binding compounds, designated staphyloferrin A and B, were detected in the culture filtrates of staphylococci grown under iron-deficient conditions. Staphyloferrin A was isolated from cultures of Staphylococcus hyicus DSM 20459. The structural elucidation of this highly hydrophilic, acid-labile compound revealed a novel siderophore, N2,N5-di-(1-oxo-3-hydroxy-3,4-dicarboxybutyl)-D-ornithine, which consists of one ornithine and two citric acid residues linked by two amide bonds. The two citric acid components of staphyloferrin A provide two tridentate pendant ligands, comprising of a beta-hydroxy, beta-carboxy-substituted carboxylic acid derivative, for octahedral metal chelation. The CD spectrum of the staphyloferrin A ferric complex indicates a predominant A configuration about the ferric ion center. The uptake of ferric staphyloferrin A by S. hyicus obeys Michaelis-Menten kinetics (Km = 0.246 microM; vmax = 82 pmol.mg-1.min-1), indicating active transport of this siderophore. The staphyloferrin A transport system is different from that of the ferrioxamines as shown by an antagonism test. Production of staphyloferrin A is strongly iron-dependent and is stimulated by supplementation of the medium with either D- or L-ornithine. DL-[5-14C]ornithine was incorporated into staphyloferrin A, demonstrating that ornithine is an intermediate in staphyloferrin A biosynthesis.

Amino Acids↗
PubMed1990

Isolation and characterization of staphyloferrin A, a compound with siderophore activity from Staphylococcus hyicus DSM 20459.

A highly hydrophilic compound was isolated from low iron culture broth of Staphylococcus hyicus DSM 20459 which exhibits siderophore activity to the producer and 37 other staphylococci. The previously unknown metabolite was designated staphyloferrin A and consists of two molecules of citric acid, each linked to D-ornitine by an amide bond. Using an ion-pair HPLC-system we detected staphyloferrin A and a second iron regulated compound (staphyloferrin B) in the culture fluid of several Staphylococcus strains. We found no evidence that staphylococci synthesize catecholor hydroxamate-type siderophores.

Chromatography, High Pressure Liquid↗
PubMed1990

Production of desferrioxamine E and new analogues by directed fermentation and feeding fermentation.

Streptomyces olivaceus TU 2718 produces the siderophore desferrioxamine E. Production depends on L-lysine and iron concentrations in the medium. With optimized conditions the yield of desferrioxamine E could be increased to 12 g/l in feeding fermentations. Supplementation of the basic production medium with natural and synthetic precursors of desferrioxamine E led to the production of twelve new analogues of desferrioxamine E.

Bacteriological Techniques↗
PubMed1990

Comparative studies on the fermentative production of lantibiotics by staphylococci.

The production of the lanthionine-containing polypeptide antibiotics gallidermin from Staphylococcus gallinarum TU 3928 and pep 5 from S. epidermidis 5 is investigated with respect to regulation and stimulation of productivity by media components, optimization of both the media used and the fermentation process and is compared to the production of the lantibiotic epidermin from S. epidermidis TU 3298. Efficient methods for rapid quantification of lantibiotics, optimization of the media and a primary enrichment by adsorption chromatography are reported.

Alanine↗
PubMed1990

Metabolic products of microorganisms. 255. Nikkomycins Wz and Wx, new chitin synthetase inhibitors from Streptomyces tendae.

Two new dipeptidyl nikkomycins of the Z and X type were isolated from the culture broth of Streptomyces tendae TU 901/395-11/32 and characterized. They show a variation in the amino acid moiety of the molecule. Nikkomycin Wz is composed of L-tyrosine and 5-amino-5-deoxy-D-allo-furanuronic acid N-glycosidally bound to uracil, whereas nikkomycin Wx is composed of L-tyrosine and 5-amino-5-deoxy-D-allo-furanuronic acid N-glycosidally bound to 4-formyl-4-imidazolin-2-one. The new nikkomycins are good inhibitors of chitin synthetase from Coprinus cinereus but they did not inhibit growth of fungi and yeasts.

Aminoglycosides↗
PubMed1989

Metabolic products of microorganisms. 252. Isolation of new nikkomycins from Streptomyces tendae.

Two new nikkomycins were isolated from the culture broth of Streptomyces tendae Tü 901/PF 53+-3. The new compounds are the dipeptide nikkomycin pseudo-Z (psi Z) and tripeptide nikkomycin pseudo-J (psi J), which are analogues to nikkomycins Z and J. Nikkomycins pseudo-Z and pseudo-J have a C-glycosidic linkage between uracil and 5-amino-5-deoxy-D-allo-furanuronic acid, which is comparable to the C-glycosidic bond in pseudouridine. The new Cc-nucleoside nikkomycins exhibit a lower biological activity than the CN-nucleoside nikkomycins.

Aminoglycosides↗
PubMed1989

Metabolic products of microorganisms. 254. Structure of the new nikkomycins pseudo-Z and pseudo-J.

Two new nikkomycins were isolated from the fermentation broth of Streptomyces tendae Tü 901/PF 53+-3. These new metabolites, nikkomycins pseudo-Z (psi-Z,1) and pseudo-J (psi-J, 2) differ from the corresponding nikkomycins Z and J by a C-glycosidic bond between C-5 of uracil and C-1' of 5-amino-5-deoxy-D-allo-furanuronic acid instead of an N-glycosidic bond. The structure elucidation was achieved by two-dimensional NMR techniques and mass spectrometry.

Aminoglycosides↗
PubMed1989

Isolation of Streptomyces tendae mutants with an altered nikkomycin spectrum.

To isolate Streptomyces tendae mutants blocked in the biosynthesis of the nikkomycin nucleoside base 4-formyl-4-imidazoline-2-one, an assay was developed to detect the formation of nikkomycins containing this base during growth on solid medium. The assay is based on the reaction of the 4-formylimidazolone structure of nikkomycins with the aldehyde reagent barbituric acid leading to red-colored products. Among 18,000 N-methyl-N'-nitro-N-nitrosoguanidine treated clones tested in the barbituric acid assay, we isolated one mutant which was incapable of forming any nikkomycins containing the 4-formylimidazolone base (nikkomycins Cx, X and I) but instead produced nikkomycins containing uracil (nikkomycins C, Z and J). In addition, we isolated strains with mutations affecting the biosynthesis of 2-amino-4-hydroxy-4-(5-hydroxy-2-pyridyl)-3-methylbutyric acid, the unusual amino acid of nikkomycins Z, X, J and I. By analyzing colonies derived from single spores or protoplasts of S. tendae Tü901/395, a mutant producing besides nikkomycins Z, X, J and I, also nikkomycins Kz/Kx and Oz/Ox, we obtained strains which only formed nikkomycins Kz/Kx and Oz/Ox with 2-amino-4-hydroxy-4-(2-pyridyl)butyric acid and 2-amino-4-hydroxy-4-(5-hydroxy-2-pyridyl)-butyric acid as amino acids. Mutation of such a strain (Tü901/395-11) by UV365nm in the presence of 8-methoxypsoralen and selection of S-2-aminoethyl-L-cysteine-resistant clones led to the isolation of Tü901/AEC1 and AEC2 which produced exclusively nikkomycins Kz and Kx. According to their nikkomycin spectrum, these strains were blocked at the hydroxylation step occurring at the pyridyl residue during biosynthesis of the nikkomycin amino acid.

Aminoglycosides↗
PubMed1988

Gallidermin: a new lanthionine-containing polypeptide antibiotic.

Gallidermin is a new member of the class of lanthionine-containing peptide antibiotics, which are summarized under the common name lantibiotics. The lantibiotic gallidermin is produced by Staphylococcus gallinarum (F16/P57) Tü3928, and it exhibits activities against the Propionibacteria, involved in acne disease. Gallidermin differs from the recently discovered tetracyclic 21-residue peptide antibiotic epidermin only in a Leu/Ile exchange in position 6. The isolation procedures for gallidermin included adsorption directly from the culture broth, ion-exchange chromatography of the amphiphilic and basic polypeptide followed by desalting, and final purification by reversed-phase HPLC. The structural elucidation of the polypeptide containing four thioether bridges involved mainly a combination of automated gas-phase sequencing, thermospray liquid chromatography/mass spectrometry and fast-atom-bombardment mass spectrometry.

Alanine↗
PubMed1988

Prepeptide sequence of epidermin, a ribosomally synthesized antibiotic with four sulphide-rings.

The genetic basis for the biosynthesis of large polypeptide antibiotics such as nisin has not been explained so far. We show here that the structural gene epiA encoding the antibiotic epidermin from Staphylococcus epidermidis is located on a 54-kilobase plasmid and codes for a 52-amino-acid prepeptide, which is processed to the tetracyclic 21-peptide amide antibiotic. The mature sequence of epidermin corresponds to the C-terminal 22-peptide segment of pre-epidermin and contains the precursor amino acids Ser, Thr and Cys, from which the unusual amino-acid constituents are derived. The more lipophilic epidermin is cleaved at a hydrophilic turn between Arg-1 and Ile+1 from the N-terminal segment-30 to -1, which probably assumes a partially amphiphilic alpha-helix conformation. We propose that the N-terminus (-30 to -1) plays a cooperative role during modification reactions and prevents toxicity of the mature epidermin to the producing strain before the antibiotic is cleaved off and secreted.

Amino Acid Sequence↗
PubMed1988

Metabolic products of microorganisms. 249. Tetracenomycins B3 and D3, key intermediates of the elloramycin and tetracenomycin C biosynthesis.

Tetracenomycins B3 and D3, besides tetracenomycin D (D1), were produced by a blocked mutant of the elloramycin producer Streptomyces olivaceus TU 2353. The compounds were isolated as red powders, and their structures were elucidated by comparing their physicochemical data with those of the known tetracenomycins A2, B1, B2, D and E. Tetracenomycin B3 (2), the main compound, and tetracenomycin D (3) were antibiotically inactive against Gram-positive and Gram-negative bacteria, whereas tetracenomycin D3 (1) showed a moderate activity against Bacillus subtilis and Arthrobacter aurescens. Tetracenomycin B3 (2) is the key intermediate where the biosynthesis of the elloramycins branches off from the line leading to tetracenomycin C (5) as the final product of the tetracenomycin biosynthesis branch.

Anthraquinones↗
PubMed1988

Metabolic products of microorganisms. 244. Colabomycins, new antibiotics of the manumycin group from Streptomyces griseoflavus. I. Isolation, characterization and biological properties.

The yellow colabomycins A to C, three new antibiotics of the manumycin group produced by Streptomyces griseoflavus (strain Tü 2880), were detected by chemical screening. They were isolated from mycelium extracts by column chromatography on various adsorbents, followed by preparative reversed phase HPLC. The main compound, colabomycin A (1), was characterized and shown to be chiefly biologically active against Gram-positive bacteria and stem cells of murine L1210 leukemia.

Alkenes↗