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Biomedical subjects

U Sankawa

Publications and source records attributed to U Sankawa.

At least 55 records · Page 3Linked to original sources
PubMed1992

Cloning of aklavinone biosynthesis genes from Streptomyces galilaeus.

Aklavinone is an aglycone of aclacinomycin A which is an important antitumor drug. Genes for the biosynthesis of aklavinone were cloned from Streptomyces galilaeus 3AR-33, an aklavinone-producing mutant, by use of the actI and actIII polyketide synthase gene probes. Restriction mapping and Southern analysis of the DNA cloned in a lambda phage vector established that the DNA represented three different regions of the S. galilaeus 3AR-33 genome that contained 3.4, 2.5, and 4.1 kb BamHI fragments which hybridized with actIII. Of those, only the 3.4 kb fragment also hybridized with actI. Complementation experiments with specifically blocked mutants confirmed that the cloned 3.4 kb BamHI fragment contains the genes required for the early stage of polyketide synthesis in aklavinone biosynthesis.

Antibiotics, Antineoplastic↗
PubMed1991

Isolation, sequence and bacterial expression of a cDNA for chalcone synthase from the cultured cells of Pueraria lobata.

cDNA clones for chalcone synthase (CHS) of Pueraria lobata cultured cells were isolated by screening the cDNA library using CHS cDNA of Phaseolus vulgaris as a probe. Analysis of nucleotide sequences of the cloned cDNA revealed a 1170-bp open reading frame that encoded a 390-amino acid polypeptide with an Mr of 43,000. The full-length cDNA was cloned into the expression vector pT7-7. CHS activity was found in the crude extracts of transformed E. coli after induction and two protein bands of ca. 43 and 34 kd were hybridized with anti-persley CHS antiserum.

Acyltransferases↗
PubMed1991

Purification and some properties of squalene-2,3-epoxide: lanosterol cyclase from rat liver.

Squalene-2,3-epoxide: lanosterol cyclase was purified from rat liver in five steps as a soluble and homogeneous protein. The purified enzyme showed a single band on SDS-polyacrylamide gel electrophoresis with a molecular weight of 75 kD. In its native state it behaved as a homo-dimer. The isoelectric point of 5.5 and the apparent Km value for (3S)-squalene-epoxide of 55 microM were estimated for the cyclase.

Animals↗
PubMed1991

Synergistic action of phenolic signal compounds and carbohydrates in the induction of virulence gene expression of Agrobacterium tumefaciens.

Virulence (vir) gene expression of Agrobacterium tumefaciens is activated by plant phenolic compounds such as alpha-hydroxyacetosyringone (HOAS), acetosyringone (AS), methyl syringate, coniferyl alcohol and sinapyl alcohol. Inositol was found to be a potentiating factor of vir-inducing activity, which enhanced the vir-inducing activity of AS and HOAS in a synergistic manner, in particular at a low concentrations of AS and HOAS. Of the other sugars tested D-glucose, L-rhamnose, D-xylose and D-galacturonic acid, the main components of plant cell wall polysaccharides, remarkedly potentiated the vir-inducing activity of AS, indicating the cooperative action of the signal compounds and sugars in Agrobacterium infection to plants.

Agrobacterium tumefaciens↗
PubMed1991

Biologically active constituents of Arnebia euchroma: structure of arnebinol, an ansa-type monoterpenylbenzenoid with inhibitory activity on prostaglandin biosynthesis.

Three phenolic compounds were isolated from the roots of Arnebia euchroma as inhibitors of in vitro prostaglandin biosynthesis. Two known compounds were identified as shikonofurans and des-O-methyllasiodiplodin. The other new compound was named arnebinol and its structure was elucidated as a novel ansa-type monoterpenylbenzenoid derivative.

Animals↗
PubMed1991

Biologically active constituents of Arnebia euchroma: structures of new monoterpenylbenzoquinones: arnebinone and arnebifuranone.

Two quinonic compounds, arnebinone and arnebifuranone, were isolated from the roots of Arnebia euchroma and their structures were elucidated on the basis of spectral evidence. Arnebionone is a monoterpenyl-benzoquinone in which the monoterpene moiety forms a fused ring to the benzoquinone. Arnebifuranone is another monoterpenylbenzoquinone with a furan ring containing side chain which is bonded to the benzoquinone at the head carbon of C10 moiety originating from the geranyl moiety of geranylhydroquinone.

Animals↗
PubMed1991

Biologically active constituents of Magnolia salicifolia: inhibitors of induced histamine release from rat mast cells.

The extracts of the flower buds of Magnolia salicifolia showed remarkable anti-allergy effects in passive cutaneous anaphylaxis (PCA) test. The bioactive constituents of this medicinal drug were isolated by monitoring their activities with an in vitro bioassay system measuring inhibitory effects on induced histamine release from rat mast cells. Of the ten isolated compounds magnosalicin is a new compound of neolignan structure. In addition to the isolated compounds samples of coumarins and lignans were evaluated their biological activities with the in vitro bioassay.

Animals↗
PubMed1991

Biologically active constituents of Centipeda minima: sesquiterpenes of potential anti-allergy activity.

Ether, methanol and aqueous extracts of Centipeda minima (Compositae) herbs were found to have significant anti-allergy activities in passive cutaneous anaphylaxis (PCA) test. Three flavonoids, two sesquiterpene lactones and an amide were isolated from this plant material as inhibitors to induced histamine release from mast cells. The sesquiterpenes were identified as isobutyroylplenolin and senecioylplenolin by spectral investigations. The flavonoids and sesquiterpenes exhibited significant anti-allergy activity in PCA test with p.o. administration.

Animals↗
PubMed1991

Biologically active constituents of Melaleuca leucadendron: inhibitors of induced histamine release from rat mast cells.

Chloroform and methanol extracts of the fruits of Melaleuca leucadendron strongly inhibited histamine release from rat mast cells induced by compound 48/80 or concanavalin A. Ursolic acid, a triterpene, was the most active compound contained in the chloroform extract and two stilbenes, piceatannol and oxyresveratrol, were isolated as active compounds from the methanol extract. Several other stilbenes and related compounds were examined to obtain information on the structure activity relationships of stilbenes.

Animals↗
PubMed1991

Identification of emodinanthrone oxygenase in fungus Aspergillus terreus.

Emodinanthrone oxygenase, which catalyzes the oxidation of emodinanthrone to emodin, has been identified in fungus, Aspergillus terreus. The fixation of an oxygen atom at the C-10 position of emodinanthrone from molecular oxygen catalyzed by the enzyme was proved by the 18O2 incubation experiment and analyses of the product emodin by mass spectrometry and nuclear magnetic resonance. The fact that the reaction did not require any foreign electron donor suggested the involvement of internal monooxygenase. Emodinanthrone oxygenase activities were found in other microbes which produce anthraquinone related metabolites.

Aspergillus↗
PubMed1990

Reaction mechanism of oxidative rearrangement of flavanone in isoflavone biosynthesis.

Microsomes that were prepared from elicitor-treated Pueraria lobata cell cultures catalyzed the conversion of liquiritigenin, a flavanone, into daidzein, an isoflavone. The reaction was resolved into two steps. 2, 7, 4'-Trihydroxyisoflavonone was formed as a major product when liquiritigenin was incubated with carefully washed microsomes in the presence of NADPH. The structure of 2, 7, 4'-trihydroxyisoflavanone was confirmed by mass and 1H NMR spectroscopies. The enzyme responsible for this rearrangement reaction is a cytochrome P-450-dependent monooxygenase. Upon treatment with a soluble enzyme fraction 2, 7, 4'-trihydroxyisoflavone yielded daidzein quantitatively. The incorporation of 18O from 18O2 into the 2-hydroxy group of 2, 7, 4'-trihydroxyisoflavanone was demonstrated by the shift of molecular ion in its mass spectrum. Based on these observations a new reaction mechanism, hydroxylation associated with 1,2-migration, is proposed for the oxidative rearrangement reaction catalyzed by the cytochrome P-450 enzyme of Pueraria lobata.

Cytochrome P-450 Enzyme System↗
PubMed1989

Inhibition of adenosine 3',5'-cyclic monophosphate phosphodiesterase by flavonoids. III.

Sixty-one flavanones, twenty-six isoflavones and eight other flavonoids, obtained from Sophora tomentosa, S. flavescens, Scutellaria baicalensis and other medicinal plants or synthesized, were tested for their inhibitory activity against adenosine 3',5'-cyclic monophosphate (cAMP) phosphodiesterase from beef heart. The structure-activity relationships were investigated.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1989

The screening of Chinese crude drugs for Ca2+ antagonist activity: identification of active principles from the aerial part of Pogostemon cablin and the fruits of Prunus mume.

Hot aqueous extracts of 134 Chinese crude drugs were subjected to screening for inhibitory activity on K+ contracture of guinea pig taenia coli, and significant activity was observed in 17 crude drugs. Chemical investigations of two crude drugs, Kakko and Ubai, which originate from Pogostemon cablin and Prunus mume, respectively, were undertaken, and patchouli alcohol (I) and 5-(hydroxymethyl)-2-furaldehyde (II) were identified as their active principles, respectively.

Animals↗
PubMed1989

Inhibitory effect of disodium cromproxate on superoxide anion (O2-) generation and membrane potential changes in stimulated neutrophils.

Disodium cromproxate is an antiallergic agent. This drug (0.5-2 mmol/L) inhibited O2- production by neutrophils induced by FMLP and PMA. However, the inhibition of FMLP-induced O2- generation was more pronounced than that induced by PMA. Disodium cromproxate also counteracted the changes in membrane potential in neutrophils induced by either FMLP or PMA. The actions of disodium cromproxate differed from those of propranolol, as propranolol had no antagonistic action on membrane potential changes induced by FMLP and PMA.

Animals↗
PubMed1988

A novel anthraquinone ring cleavage enzyme from Aspergillus terreus.

An enzyme activity which catalyzes the ring cleavage of the anthraquinone questin to form benzophenone desmethylsulochrin was found in the cell-free extract of Aspergillus terreus, a (+)-geodin producer. The product was identified as desmethylsulochrin by high-resolution mass spectroscopy and chemical carrier dilution analysis. The enzyme showed an absolute requirement of NADPH and molecular oxygen. Therefore, the enzyme, named questin oxygenase, was considered to be classified as a monooxygenase. The optimum pH was around 7.5. The enzyme was very unstable and lost its activity completely after storage overnight at 4 degrees C in 0.05 M phosphate buffer, pH 7.5. The instability of the questin oxygenase was partially overcome by the addition of polyols and the non-ionic detergent Tween 80 to the buffer. By DEAE-cellulose column chromatography, two protein fractions, named DE-I and DE-II, were obtained. Neither fraction reacted with questin by itself. However, the combination of DE-I and DE-II reconstituted the questin oxygenase system to convert questin to desmethylsulochrin. This result suggested that the system is not a simple combination of oxygenase and hydrolase, but requires some additional factor(s) such as electron transfer protein.

Anthraquinones↗