PubMed Health⌕ Search

Biomedical subjects

T Takeuchi

Publications and source records attributed to T Takeuchi.

At least 91 records · Page 5Linked to original sources
PubMed1992

Cyclooctatin, a new inhibitor of lysophospholipase, produced by Streptomyces melanosporofaciens MI614-43F2. Taxonomy, production, isolation, physico-chemical properties and biological activities.

Cyclooctatin has been isolated from Streptomyces melanosporofaciens MI614-43F2 as part of a program designed to find microorganism-produced inhibitors of lysophospholipase. It was purified by chromatography on silica gel, Capcell Pak C18 (HPLC) and Sephadex LH-20 followed by solvent extraction and then isolated as a colorless powder. Cyclooctatin has the molecular formula of C20H34O3. It is competitive with the substrate, and the inhibition constant (Ki) was 4.8 x 10(-6) M.

Animals↗
PubMed1992

Production of new anthracycline antibiotics 1-hydroxy-oxaunomycin and 6-deoxyoxaunomycin by limited biosynthetic conversion using a daunorubicin-negative mutant.

A limited biosynthetic conversion of some known anthracyclinones using a specific daunorubicin-nonproducing mutant provided four new anthracycline antibiotics: 1-Hydroxy-10-methoxycarbonyl-13-deoxocarminomycin; 1-hydroxy-13-deoxocarminomycin; 1-hydroxyoxaunomycin and 6-deoxyoxaunomycin. Their isolation and purification from bioconversion broth, structural determination and antitumor activities against leukemic L1210 cells are described.

Animals↗
PubMed1992

Amino acid analogs of benanomicin A through desalaninebenanomicin A.

Desalaninebenanomicin A has been synthesized in good yield by the cleavage of the amido bond of benanomicin A using MEERWEIN's reagent. This is a useful intermediate to prepare amino acid analogs of benanomicin A. MEERWEIN's reagent reacts with totally protected benanomicin A to give a stable imino ether. After deprotection, the imino ether is treated with aqueous acetone at reflux to afford a methyl ester of desalaninebenanomicin A. Desalaninebenanomicin A was coupled with a variety of amino acids by the active ester method to afford new benanomicin analogs.

Amino Acids↗
PubMed1992

Photochemically obtained N-demethyl derivatives of anthracyclines.

New N-monodemethyl and N-didemethyl derivatives were obtained from seven N-dimethylamino sugar (rhodosamine)-containing anthracyclines by photochemical reaction and their in vitro bioactivities against L1210 cell culture were compared with those of their N-dimethyl parent compounds. N-Demethyl derivatives obtained from betaclamycin T (7-O-rhodosaminyl-beta-rhodomycinone) were much more cytotoxic while those from the other six antibiotics were rather less active as compared with their parent compounds. The N-demethylation also gave a considerably greater decrease in the inhibitory activity on RNA synthesis as compared to DNA synthesis, so that the N-demethyl derivatives showed smaller IC50 ratios on DNA/RNA than their parent compounds.

Animals↗
PubMed1992

Production of bellenamine and new metabolites in a synthetic medium.

A streptomyces antibiotic, bellenamine has been produced in a simple synthetic medium consisting of D-galactose, dextrin, ammonium sulfate and calcium carbonate. Three new minor metabolites, N-(aminomethyl)succinamic acid, 1'-N-acetylbellenamine and D-beta-lysinamide have been isolated from the synthetic medium culture. They showed no antibiotic activity.

Ammonium Sulfate↗
PubMed1992

Biosynthesis of benastatin A.

The biosynthesis of benastatin A, produced by Streptomyces sp. MI384-DF12, has been studied by feeding experiments with 14C- and 13C-labeled compounds followed by measurement of radioactivity and 13C NMR analysis. The results indicate that benastatin A is derived from two methionine units and fourteen acetate units, condensed in the "head-to-tail" fashion of typical polyketide biosynthesis.

Benz(a)Anthracenes↗
PubMed1992

Enhancement by ubenimex (bestatin) of host resistance to Candida albicans infection.

Ubenimex is a low molecular weight microbial metabolite which has been demonstrated to have antitumor and immunomodulatory activities. In this study, the protective effect of ubenimex on Candida albicans infection was investigated in normal and immunosuppressed mice. In normal mice, treatment with ubenimex at 0.5, 5 and 25 mg/kg for 5 days prior to infection prolonged survival time in a dose-dependent manner. In immunosuppressed mice treated with a single dose of cyclophosphamide 4 days prior to infection, ubenimex treatment at 5 mg/kg for 5 days significantly increased the number of survivors. Ubenimex-treated mice had a significant increase in number of peritoneal exudate cells with neutrophils as well as enhanced functions, including phagocytosis and active oxygen production. These results suggest the potential usefulness of ubenimex as a prophylactic agent for the management of patients with opportunistic fungal infections.

Animals↗
PubMed1992

Dethymicin, a novel immunosuppressant isolated from an Amycolatopsis. Fermentation, isolation, physico-chemical properties and biological activities.

In the course of screening for immunomodulators inhibiting the mixed lymphocyte culture reaction (MLCR), we found a novel immunosuppressant, dethymicin in mycelium of Amycolatopsis mediterranei MI710-51F6. From physico-chemical properties and biological activity it is different from immunosuppressants produced by microorganisms such as cyclosporins, FK506 and rapamycin. It inhibited immune responses in vitro and in vivo, and prolonged skin allograft in rats.

Actinomycetales↗
PubMed1992

Production of new anthracycline antibiotics by microbial 4-O-methylation using a specific daunorubicin-negative mutant.

Microbial 4-O-methylation using a specific daunorubicin-blocked, nonproducing mutant provided the new anthracycline antibiotics 4-O-methylbetaclamycin T, 4-O-methylyellamycin A and 4-O-methyl-13-hydroxyoxaunomycin, from which 4-O-methyloxaunomycin and 4-O-methyl-6-deoxyoxaunomycin were then prepared by further photochemical N-demethylation. Antitumor activities in vitro and in vivo against L1210 cells were compared with those of their 4-O-demethyl derivatives. It was found that all the 4-O-methyl derivatives had a markedly reduced cytotoxicity in vitro as compared with the 4-O-demethyl compounds. However, some of them were endowed with a significantly improved antitumor activity in vivo.

Animals↗
PubMed1992

Biosynthesis of bellenamine by Streptomyces nashvillensis using stable isotope labeled compounds.

The biosynthesis of bellenamine was studied by feeding 13C and 15N labeled precursors to the synthetic medium culture of Streptomyces nashvillensis MD743-GF4. The high degree of incorporation of D-[1-13C]beta-lysine indicated that it is a direct intermediate, while supplemented L-beta-lysine repressed the production of bellenamine. [2-13C]Glycine was well incorporated into the C-1' of the open-chain aldoaminal structure. All four nitrogens of bellenamine were derived from [15NH4]2SO4 present in the synthetic medium. In the addition of L-lysine and glycine, [15NH4]2SO4 was highly incorporated into CONH. The feeding experiments of 13C labeled acetates suggested that the D-beta-lysine moiety was derived from L-lysine by catalysis of a new 2,3-aminomutase, and L-lysine was biosynthesized from acetates via the TCA cycle and diaminopimelic acid pathway.

Acetates↗
PubMed1992

Preparation of 13C and 15N labeled bellenamine and its degradation products.

A streptomyces metabolite, bellenamine, has been converted into D-beta-lysinamide and cyclized bellenamine in an acidic solution at 75 degrees C. The structure of the new cyclized compound was assigned as (R)-6-(3-aminopropyl)-1,3-diazacyclohexan-4-one by spectral analyses. [1-13C, Amide, 1'-15N2]bellenamine, which has been isolated from the culture by feeding both L-[1-13C]lysine and [15NH4]2SO4 to a synthetic medium, was degraded under acidic condition to obtain the stable isotope labeled D-beta-lysine, D-beta-lysinamide and cyclized bellenamine. These labeled compounds were analyzed by 13C and 15N NMR spectra, and will be used for the biosynthetic study on bellenamine.

Ammonium Sulfate↗