p34cdc2 kinase plays a key role in the initiation of mitosis. The activity of this kinase requires the binding of a protein, named cyclin, to it. The kinase forms a heterodimer with cyclin. Cyclin A or cyclin B is the counterpart of this complex. The differences in the activity between cyclin A/cdc2 kinase and cyclin B/cdc2 kinase have not been cleared. In recent years, the other cdc2-like kinases were identified. One of them was CDK2 (cyclin dependent kinase 2). CDK2 could rescue the defect of the budding yeast CDC28 mutation, which arrested the cells at a point named START, in G1 phase. Then, CDK2 was thought to be worked at G1 through S phase in a cell cycle, but the details on the role of this kinase has not been cleared so far. In this study, we separated the human cyclin A/cdc2 kinase, cyclin B/cdc2 kinase and CDK2, each other by use of column chromatography, and characterized the each kinase. These kinases had the same substrate specificities when the synthesized peptides were tested. They phosphorylated the threonine residue in the sequence -Thr-Pro-Lys-Lys-Ala- but hardly phosphorylated threonine residue the sequence -Thr-Pro-Lys-Ala-Lys-. They had some differences in the substrate-proference when the native proteins were tested. In a cell cycle of human cells, the activity of cdc2 kinase increased at G2/M phase and the activity of CDK2 was high from S through M phase. These data suggested that cdc2 kinase works at the transition from G2 to M phase and that CDK2 works from G1 through G2/M phase. They could phosphorylate different protein-substrates having the common phosphorylated sequence -Thr-Pro-X-Lys-.
Plant cell cultures are potentially rich sources of useful phytochemicals but relatively few cultures can synthesize these metabolites. Expression of genetic informations on the secondary metabolism is thought to be generally repressed in such actively proliferating cells. It would be beneficial to be able to "switch on" the repressed activities by the addition of a specific inducer to these cultures but the control mechanism is, at present, only poorly understood. Microbial infection often induces the production of antibiotic substances in plant cells and the molecules which stimulate their synthesis have been called elicitors. The elicitors include various carbohydrates and glycoproteins derived from the cell walls of fungi and plants. These molecules may bind to certain receptor site on the surface of plant cells. We obtained evidence showing that these receptors transduce the external stimuli into an intracellular signal system partly via activation of phosphoinositol cycle as in animal cells, and partly via activation of adenylate cyclase which converts ATP into cAMP. In the latter case, cAMP stimulates Ca2+ influx from external space without participating cAMP-dependent protein kinase. These processes activate various Ca2+ (and calmodulin)-dependent protein kinases by increasing the level of free Ca2+ in the cytoplasm and somehow trigger the cellular responses which may include alterations in gene expression. Recent studies suggest that the increased synthesis of secondary metabolites in response to elicitation of various types appears to be not limited to the defense mechanism but the general response of cultured plant cells.
By the reaction of 2-benzoylmethylimidazoles (1a, b) with polarized olefins (2, 3) in the presence of K2CO3, the corresponding imidazo [1, 2-a] pyridine derivatives (4, 5) were obtained. Methylsulfinylimidazopyridine derivative (7) obtained by the reaction of 5b with m-chloroperbenzoic acid (m-CPBA), easily underwent nucleophilic substitution to give the corresponding substituted compounds (8a-e). The substitution of chloroimidazopyridine derivative (11) with nucleophiles produced the corresponding substituted compounds (12a-d).
Protective effects of 41 Taiwan crude drugs on rat hepatic injuries caused by carbon tetrachloride (CCl4) and α-naphthylisothiocyanate (ANIT) were investigated. The methanol extracts of Elephantopi Herba and Lonicerae Flos inhibited the release of intrahepatic enzymes and histological changes by CCl4. The methanol extracts of Canarii Radix, Arecae Pericarpium, Cynomorii Caulis, Polygoni Cuspidati Radix, Phyllodii Herba, Junci Caulis Medulla, Rubiae Herba and Rhinacanthi Herba protected the hepatic injury by ANIT. Among them, the water extracts of Cymorii Caulis and Junci Caulis Medulla showed higher protective potency than the methanol extracts. And them this two crude drugs also protected the cholestasis by ANIT.
A simple and precise method was established for the simultaneous determination of daidzin and puerarin and the determination of daidzein in oriental pharmaceutical decoctions containing Puerariae Radix using high-performance liquid chromatography with tetra-n-heptylammonium bromide (THA) as an ion-pair reagent. Daidzin and puerarin were eluted within 45 min without interference with co-existing components using an ODS column and a mixture of 10 mM phosphate buffer (pH 6.5)-methanol (68 : 32) containing 5 mM THA as a mobile phase. Daidzein was eluted within 35 min without interference with co-existing components using an ODS column and a mixture of 10 mM phosphate buffer (pH 6.5)-acetonitrile (72 : 28 or 68 : 32) containing 5 mM THA as a mobile phase.
1, 3-Dimethyl-2-indolinone gave meso and racemic dimers by the oxidative dimerization reaction. Conformations of these dimers were examined in solid and solution, respectively. The meso isomer kept the ±sc conformation both in solid and solution. But the racemic isomer showed the -sc conformation in solution, which was confirmed by the nuclear Overhauser effect experiments in the 1H-NMR. We also showed that the -sc conformation in solution was different from that in solid. We measured the +sc conformation in solid by X-ray analysis.
A simple method using ion-pair high-performance liquid chromatography was established for the rapid and precise determination of honokiol (3', 5-di-2-propenyl-1, 1'-biphenyl-2, 4'-diol) and magnolol (5, 5'-di-2-propenyl-1, 1'-bi-phenyl-2, 2'-diol) in eighteen species of oriental pharmaceutical decoctions containing Magnolia bark. An ODS column and a mixed solvent system of water involving 10 mM tetra-n-amylammonium bromide (TAA) and acetonitorile (4 : 6) as a mobil phase were used for the separation. Honokiol and magnolol were eluted without interference of other coexisting components within 12 min.