Metabolism of Steviol and Its Derivatives by Gibberella fujikuroi

Steviol (ent-13-hydroxykaur-16-en-19-oic acid)* is metabolized by Gibberella fujikuroi in the presence of inhibitors of gibberellin biosynthesis, such as quaternary ammonium salt-type growth retardants, to afford 7β-Miydroxy- and 6β,7β-dihydroxysteviol, gibberelhns A₁, A₁₈, A₁₉, A₅₃ and 7β,13-dihydroxykaurenolide. Steviol acetate (ent-13-acetoxykaur-16-en-19-oic acid) is also metabolized to the 6β,7β-dihydroxy-derivative and to the 13-acetyl derivatives of gibberellins A₁₇ and A₂₀ and steviol methyl ester (methyl ent-13-hydroxykaur-16-en-19-oate) into the monohydroxy-, dihydroxy- and hydroxyoxo-derivatives. These results indicate a low substrate specificity of the enzymes in the fungus and provide a useful preparative methodology of several important plant gibberellins carrying the 13-hydroxyl group.     

Metabolism of [3H] Gibberellin A5 in Cell Suspension Cultures of Pharbitis nil

Gibberellin A₅ (GA₅), a native GA of immature seeds of Pharbitis nil, was fed to Pharbitis nil cell suspension cultures as [C-l, ³H] GA₅ (3.1 Ci/mmol), and its metabolism over a 48 hr period was investigated. Radioactivity in free GA metabolites was 13.1%, with 79.9% in GA glucosyl conjugate-like metabolites. Only 7.0% of the radioactivity remained as [³H] GA₅. Tentative identifications were based on comparison with retention times of authentic free GAs and/or glucosyl conjugates after sequential chromatography on Si gel partition column → gradient-eluted C18 HPLC-radiocounting (RC) → isocratic-eluted C18 HPLC-RC, and showed that [³H] GA₅ was converted to [³H] GA₁ (2%), [³H] GA₃ (4%), [³H] GA₆ (2%), [³H] GA₂₂ (1%) and their glucosyl conjugates, and also to [³H] GA₈ glucoside, and [³H] GA₅ glucosyl conjugates. The major conjugate-like substances were [³H] GA₁ and [³H] GA₃ glucosyl esters, at 15% and 34%, respectively, of the total extractable radioactivity.     

Comparison of the Key Enzymes of Hyphomicrobium sp. 53-49 under Various Growth Conditions: Aerobic,Denitrifying and Autotrophic

For Hyphomicrobium 53-49 capable of growing under various conditions, aerobic methanol, anaerobic methanol (with denitrification), autotrophic (H₂-O₂-CO₂), aerobic ethanol and aerobic acetate, investigation and comparison of the specific activities of the following enzymes were performed: alcohol dehydrogenase (NAD-ethanol linked and NAD-methanol linked), primary alcohol dehydrogenase, formaldehyde dehydrogenase (NAD-GSH linked and DCPIP linked), formate dehydrogenase, serine hydroxymethyl transferase, hydroxypyruvate reductase, isocitrate lyase (icl), malate lyase, malate dehydrogenase, ribulosebisphosphate (RuBP) carboxylase, phos-phoenolpyruvate (PEP) carboxykinase (ADP linked), PEP carboxylase (phosphorylating), pyruvate carboxylase (NADH linked and NADPH linked) and α-ketoglutarate carboxylase (NADH linked and NADPH linked). On the basis of the data obtained, it was concluded that during growth on methanol, aerobically and anaerobically, the icl+ serine pathway operated, while during autotrophic growth on H₂-O₂-CO₂, CO₂ was incorporated through the RuBP pathway and others, and during growth on ethanol or acetate, neither the serine pathway nor the RuBP pathway operated. The organism changed its metabolism through the regulation of the metabolic enzymes according to the growth conditions.     

Isolation of Triterpenoid Glycosides (Saikosaponins) from Bupleurum polyclonum Y. Li et S. L. Pan and Their Chemical Structures

Sixteen triterpenoid glycosides, named S13 to S25, S37, S38 and S40, were isolated from the root of Bupleurum polyclonum Y. Li et S. L. Pan, and their structures were determined from NMR spectral analyses. Among them, S24, S37 and S38 were found to be new substances, their structures being established as 30-β-d-glucopyranosyl 30-hydroxysaikosaponin-b₂, 2″-O-acetylsaikosaponin-b₂ and 3″-O>-acetylsaikosaponin-b₂, respectively.     

Syntheses and Biological Activities of Isonitrile Dipeptides

We investigated GroEL substrates from Bacillus subtilis 168 using the single-ring mutant of B. subtilis GroEL. We identified 28 candidates for GroEL substrates, of which Spo0B, Ald, Eno, SpoIIP, and FbaA were involved in spore formation, and Rnc, Tuf, Eno, Tsf, and FbaA were essential for B. subtilis growth. As observed at the protein level, the amount of SpoIIP interaction with GroEL increased at 3 h after initiation of sporulation.     

Ionophorous Properties of SY-1 (20-Deoxysalinomycin) in Rat Liver Mitochondri

SY-1 (20-deoxysalinomycin), a monocarboxylic polyether antibiotic closely related to salinomycin, caused a rapid release of previously accumulated alkali metal cations by valinomycin or monazomycin in rat liver mitochondria, and simultaneously reversed swelling of mitochondria.

With a strict specificity for substrate and cation, SY-1 exhibited a property of inhibiting mitochondrial functions such as substrate oxidation, oxidative phosphorylation and ATP hydrolysis induced by valinomycin or monazomycin, In comparative study with salinomycin, SY-1 was found to be more effective on the mitochondrial functions than salinomycin.

On the basis of the results so far obtained, the inhibitory effect of SY-1 on mitochondria is interpreted as a result of interaction with essential cations, especially with K⁺, in mitochondria.     

Isolation and Characterization of Plant Growth Substances in Immature Seeds and Etiolated Seedlings of Phaseolus vulgaris

From the immature seeds of Phaseolus vulgaris cv. Kentucky Wonder GA₁, GA₈, GA₃₈, ABA and GA₈ glucoside were isolated, and GA₄, GA₅, GA₆ and GA₃₇ were identified by GC or GC-MS. Unknown substance, AB–II, was also suggested to be present in the immature seeds. In the etiolated seedlings glucosyl esters of GA₁ and GA₃₈ were identified by GC. GA₈ glucoside and AB–II were shown to be present by the histograms.     

Solubilization and Characterization of Ovomucin without Chemical Modification

1. The egg white, thick and thin fractions, was solubilized in 1.0% SDS solution by vigorous mixing and subjected to gel filtration on a Sepharose 4B column, eluted with 1.0% SDS. The isolated thick and thin ovomucins were found by analytical disc electrophoresis to be free from contamination with lysozyme.

2. In the velocity sedimentation the two ovomucin fractions behave similarly, both comprising at least two components with sedimentation coefficients 35 S and 30 S.

3. The chemical compositions of the two ovomucin fractions showed only notable difference in that the carbohydrate content of the thick white ovomucin was somewhat higher than that of the thin white ovomucin. The amino acid profiles of the two fractions were similar.

     

Isolation and Characterization of a Free Gibberellin and Glucosyl Esters of Gibberellins in Mature Seeds of Phaseolus vulgaris

Treatment of N⁶,N⁶,5′-O-tribenzoyl-2′,3′-O-isopropylidenetubercidin (VI) with aqueous acetic acid afforded N⁶,5′-O-dibenzoyltubercidin (V), which was mesylated to yield the dimesylate X. On treatment of X with sodium iodide and zinc dust, the 2′,3′-unsaturated derivatives of tubercidin XI and XIII were obtained.

N⁶,5′-O-Dibenzoyltubercidin 2′,3′-thionocarbonate (XIV), prepared from V by treatment with Corey-Winter reagent, was converted to the 1-methyl-2′,3′-unsaturated derivative XV in refluxing trimethyl phosphite.     

A Screening Procedure on the Inhibitors of Substrate-incorporation in Tumor Cells Methodological Survey and Its Evaluation

A comparative study of inhibition on the substrate-incorporation in several species of tumor cells has been achieved in combination with the antibiotics having different action mechanisms. It was thus revealed that a large part of the antitumor antibiotics so far examined showed a marked inhibitory response even at a low concentration. Particularly, the antibiotics whose action mechanism were established primarily on cell membrane were markedly sensitive. An apparent difference in the sensitivity was observed in some groups of antitumor antibiotics which act on nucleic acid synthesis. A methodological survey together with an evaluation of this procedure is discussed.