Masana Noma

The alkaloid contents of sixty Nicotiana species

Abstract The alkaloid content (nicotine, nornicotine, anabasine, and anatabine) in leaves and roots of 60 Nicotiana species were analyzed by GC. All species contained alkaloids, the amounts varying with the species. There was no clearcut correlation between alkaloid amounts and subgeneric or sectional classification. The alkaloid content in the floral parts and immature and mature fruits of Nicotiana tabacum were also analyzed.

Morphological changes and hypomethylation of DNA in transgenic tobacco expressing antisense RNA of the S-adenosyl-l-homocysteine hydrolase gene

S-adenosyl-l-homocysteine hydrolase (SAHH) is a key enzyme in the regulation of intracellular methylation reactions. To investigate the role of SAHH in methylation reactions and morphogenesis in planta, we have made transgenic plants expressing antisense RNA of tobacco SAHH. The transgenic plants displayed distinct morphological changes including a floral homeotic change. We hypothesized that the changes were caused by increased levels of cytokinin. In those transgenic plants, we observed that a repetitive DNA sequence appeared less methylated than controls. We speculated that altered gene expressions by the hypomethylation of DNA might be involved in the changes.

Occurrence of nicotianamine in higher plants

Abstract Nicotianamine is present in highest concentration in growing leaf tissue and has been found not only in the Solanaceae but also in the Liliaceae and Gramineae.

Promotion of flowering in apple trees with gibberellin A4 and C-3 epi-gibberellin A4

The proportion of spurs flowering on apple trees (Malus domestica Borkh. cv Golden Delicious) displaying a high degree of alternate-year flowering was increased in the “off” year by gibberellin A4 (GA4) and C-3 epi-GA4 applied in the previous year. When applied 4.5 weeks after anthesis amounts of GA4 ranging from 3 to 300 μg per spur and 25 or 50 μg of C-3 epi-GA4 per spur were effective. Treatments with GA4 made seven weeks after anthesis were less effective. A combination of 30 μg GA4 and 30 μg zeatin (6-(4-hydroxy-3-methylbut-trans-2-enylamino)purine) promoted flowering at both treatment times, and tended to be more effective than GA4 alone.

Sequence analysis of the agaB gene encoding a new β-agarase from Vibrio sp. strain JT0107

An agarase gene (agaB) was cloned from genomic DNA of Vibrio sp. strain JT0107. Analysis of the 3200 nucleotide sequence just before the agarase 0107 gene (agaA) which existed in genomic DNA of Vibrio sp. strain JT0107 revealed a putative single open reading frame coding for 955 amino acids. Comparison of the deduced amino acid sequence of AgaB to that of agarase 0107 revealed the existence of partially highly homologous regions. A part of this gene was expressed in Escherichia coli to yield a protein with agarase activity. This is the first report of evidence by genetic analysis that at least two different kinds of agarases exist in strain JT0107.

Endotoxin transduces Ca2+ signaling via platelet‐activating factor receptor

Lipopolysaccharide (LPS) is a pathogenic substance causing severe multiple organ failures and high mortality, Although several LPS binding proteins have been identified, the molecular mechanism underlying the LPS signaling pathway still remains obscure. We have found that the LPS‐induced Ca2+ increase in platelets and platelet aggregation is blocked by selective platelet‐activating factor (PAF) receptor antagonists, thus suggesting a cross‐talk between LPS and the PAF receptor. Next, we confirmed this hypothesis using the cloned PAF receptors [(1991) Nature 349, 342–346; (1991) J. Biol. Chem. 266, 20400–20405] expressed in Xenopus occytes and Chinese hamster ovary (CHO) cells. In both systems, cells responded to LPS only when PAF receptors were expressed, and specific PAF binding was successfully displaced and reversibly dissociated by LPS. PAF receptor activation by LPS may represent a novel important pathway in the pathogenesis of circulatory collapse and systemic thrombosis caused by endotoxin.

Human 5-lipoxygenase associates with phosphatidylcholine liposomes and modulates LTA4 synthetase activity

A Ca2+ and a phosphatidylcholine (PC) as stimulatory factors to human 5-lipoxygenase (5-LO) were assessed to examine aspects of the regulatory mechanism of 5-LO. In the presence of Ca2+ (1 microM or less), PC liposomes distinctly stimulated the dual activities of 5-LO for the production of 5-HPETE from arachidonate and for its subsequent conversion to LTA4. At the same concentration of Ca2+, 5-LO was found to bind to PC liposomes. As with 5-LO activities, the binding was dependent on the range of Ca2+ concentration. The conversion ratios of 5-HPETE to LTA4 were dependent on PC liposome concentration and reached a maximum of 50% conversion. Among the four cell membrane lipids examined, PC liposomes demonstrated the highest conversion ratio of 5-HPETE to LTA4 by 5-LO. Most of the arachidonate added to the reaction mixture localized in PC liposomes. These results confirm that the intracellular increase of Ca2+ concentration causes 5-LO to associate with the cell membrane and perform an interfacial reaction. They also suggest that this binding of 5-LO to the cell membrane enhances the subsequent conversion from 5-HPETE to LTA4.

Mutagenesis studies on the amino acid residues involved in the iron-binding and the activity of human 5-lipoxygenase

Human 5-lipoxygenase contains a non-heme iron essential for its activity. In order to determine which amino acid residues are involved in the iron-binding and the lipoxygenase activity, nine amino acid residues in highly homologous regions among the lipoxygenases were individually replaced by means of site-directed mutagenesis. Mutant 5-lipoxygenases in which His-367 or His-550 was replaced by either Asn or Ala, His-372 by either Asn or Ser, or Glu-376 by Gln were completely devoid of the activity. Though mutants containing an alanine residue instead of His-390 or His-399 lacked the activity, the corresponding asparagine substituted mutants exhibited. The other mutants retained the enzyme activity. These results strongly suggest that His-367, His-372, His-550 and Glu-376 are crucial for 5-lipoxygenase activity and coordinate to the essential iron.

Expression of human 5‐lipoxygenase cDNA in Escherichia coli

A cDNA for human 5‐lipoxygenase (5LO) was inserted into the vector pKC (constructed from pKK223‐3 by replacing its replication origin with that of pUC18) and expressed in Escherichia coli. The enzyme expressed was purified to homogeneity from the cellular soluble fraction. The purified enzyme showed both 5LO and leukotriene A4 synthase activities, which were stimulated by Ca2+ and ATP. Its molecular mass (78 kDa) and NH2‐terminal sequence were identical with those of 5LO purified from human leukocytes. The availability of the expression system will facilitate further studies on its regulation and the reaction mechanism of the enzyme.

Bioactive Marine Metabolites. Part 13. Kabiramide C, a Novel Antifungal Macrolide from Nudibranch Egg Masses.

The structure of the title compound (I) is elucidated by IR, UV and 1H- and 13C-NMR spectroscopy.