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91.
1. Five and four tryptophan residues in Taka-amylase A [EC 3.2.1.1] of A. oryzae (TAA) were modified with dimethyl(2-hydroxy-5-nitrobenzyl)-sulfonium bromide (K-IWS) in the absence and the presence of 15% maltose (substrate analog), respectively. Only one tryptophan residue was modified with dimethyl(2-methoxy-5-nitrobenzyl)-sulfonium bromide (K-IIWS) irrespective of the presence or absence of maltose. Kinetic parameters (molecular activity, k0, Michaelis constant, Km, and inhibitor constant, Ki) of the enzyme modified with K-IWS and K-IIWS were determined. The k0 value decreased with increase in the number of modified residues, but Km and Ki values and the type of inhibition were not altered by the modification. 2. The fluorescence quenching reaction of TAA with N-bromosuccinimide (NBS) proceeded in three phases. The second-order rate constants of the three phases were determined to be (4.3 +/- 0.5) x 10(5) M-1 . s-1, (2.1 +/- 0.3) x 10(3) M-1 . s-1 and (1.7 +/- 0.2) x 10(2) M-1 . s-1, respectively. In the presence of maltose, the first phase was further separated into two phases with rate constants of (4.6 +/- 0.6) x 10(6) M-1 . s-1 and (6.9 +/- 1.1) x 10(4) M-1 . s-1, respectively. On the basis of the results, it is estimated that five out of nine tryptophan residues are accessible to the solvent and among them, two tryptophan residues are substantially exposed: one is located in the maltose binding site near the catalytic site (its modification affects the catalytic function), and the other exists on the enzyme surface far from the active site. 相似文献
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94.
Motohara M Ibuki K Miyake A Fukazawa Y Inaba K Suzuki H Masuda K Minato N Kawamoto H Nakasone T Honda M Hayami M Miura T 《Microbes and infection / Institut Pasteur》2006,8(6):1539-1549
One of the mechanisms by which HIV infection induces the depletion of CD4+ T cells has been suggested to be impairment of T-cell development in the thymus, although there is no direct evidence that this occurs. To examine this possibility, we compared T-cell maturation in the intrathymic progenitors between macaques infected with an acute pathogenic chimeric simian-human immunodeficiency virus (SHIV), which causes profound and irreversible CD4+ T-cell depletion, and macaques infected with a less pathogenic SHIV, which causes only a transient CD4+ T-cell decline. Within 27 days post-inoculation (dpi), the two virus infections caused similar increases in plasma viral loads and similar decreases in CD4+ T-cell counts. However, in the thymus, the acute pathogenic SHIV resulted in increased thymic involution, atrophy and the depletion of immature T cells including CD4(+)CD8(+) double-positive (DP) cells, whereas the less pathogenic SHIV did not have these effects. Ex vivo differentiation of CD3(-)CD4(-)CD8(-) triple-negative (TN) intrathymic progenitors to DP cells was assessed by a monkey-mouse xenogenic fetal thymus organ culture system. Differentiation was impaired in the TN intrathymic progenitors of the acute pathogenic SHIV-infected monkeys, while differentiation was not impaired in the TN intrathymic progenitors of the less pathogenic SHIV-infected monkeys. These differences suggest that dysfunction of thymic maturation makes an important contribution to the irreversible depletion of circulating CD4+ T cells in vivo. 相似文献
95.
Hao HF Takaoka M Bao XH Wang ZG Tomono Y Sakurama K Ohara T Fukazawa T Yamatsuji T Fujiwara T Naomoto Y 《Biochemical and biophysical research communications》2012,423(4):744-749
Peritoneal dissemination is one of the most terrible types of colorectal cancer progression. Focal adhesion kinase (FAK) plays a crucial role in the biological processes of cancer, such as cell attachment, migration, proliferation and survival, all of which are essential for the progression of peritoneal dissemination. Since we and other groups have reported that the inhibition of FAK activity exhibited a potent anticancer effect in several cancer models, we hypothesized that TAE226, a novel ATP-competitive tyrosine kinase inhibitor designed to target FAK, can prevent the occurrence and progression of peritoneal dissemination. In vitro, TAE226 greatly inhibited the proliferation and migration of HCT116 colon cancer cells, while their adhesion on the matrix surface was minimally inhibited when FAK activity and expression was suppressed by TAE226 and siRNA. In vivo, when HCT116 cells were intraperitoneally inoculated in mice, the cells could attach to the peritoneum and begin to grow within 24 h regardless of the pretreatment of cells with TAE226 or FAK-siRNA, suggesting that FAK is not essential, at least for the initial integrin-matrix contact. Interestingly, the treatment of mice before and after inoculation significantly suppressed cell attachment to the peritoneum. Furthermore, oral administration of TAE226 greatly reduced the size of disseminated tumors and prolonged survival in tumor-bearing mice. Taken together, a possible strategy for inhibiting peritoneal dissemination by targeting FAK with TAE226 appears to be applicable through anti-proliferative and anti-invasion/anti-migration mechanisms. 相似文献
96.
97.
H Fukazawa H Suzuki N Tanaka 《Biochemical and biophysical research communications》1985,130(3):1072-1077
5'-Nucleotide phosphodiesterase (5'-NPDase) was partially purified from plasma membranes of murine lymphoma L5178Y. The enzyme was inactivated by N-ethylmaleimide and Zn2+, but stabilized by dithiothreitol, suggesting that it is an SH enzyme. The enzyme, Km 1.54 mM, pI 5.8 and MW 23k, differs from liver 5'-NPDase in MW, Km and sensitivity to some inhibitors. On the contrary, 5'-NPDase, derived from normal mouse organs, is similar to the liver enzyme. The results suggest that tumor cells possess a novel molecular species of 5'-NPDase. 相似文献
98.
Takao K Miyatake S Fukazawa K Wada M Sugita Y Shirahata A 《Analytical biochemistry》2008,376(2):277-279
We developed a nonradioactive assay to measure spermidine/spermine N1-acetyltransferase (SSAT) activity by high-performance liquid chromatography (HPLC). N1-dansylnorspermine was prepared and evaluated as a substrate of acetylation with acetyl-CoA by SSAT in rat hepatoma (HTC) cells. Kinetic studies revealed that the Km values of N1-dansylnorspermine and acetyl-CoA were approximately 11 and 13 μM, respectively. When the assay method was applied to HTC cell samples, the SSAT activity, even at the control level, could easily be detected in as few as 20 μg protein of cell extract corresponding to 1 × 105 cells per determination, and 100 samples could be analyzed overnight. Thus, our HPLC method is a rapid and sensitive assay for the measurement of SSAT activity. 相似文献
99.
Harman (1-methyl-9H-pyrido[3,4-b]indole) reacted readily with sodium hypochlorite in an aqueous medium to give the mono-chlorinated derivatives, which reportedly have greater co-mutagenic activity than harman in the presence of o-toluidine toward Salmonella typhimurium TA 98 with S9 mix. Mono-chlorinated harmans were detected by concentration using blue rayon (BR) and GC/MS analysis in the final effluent from a sewage treatment plant in Shizuoka, Japan. The amounts adsorbed for 24h were 1-45ng/gBR for mono-chlorinated harman and 110-730ng/gBR for harman. 相似文献
100.
Nong VH Arahira M Phan VC Kim CS Zhang D Udaka K Fukazawa C 《Journal of biochemistry》2002,132(2):291-300
Molecular characterization of plant group II chaperonin (CCT, c-cpn, or TriC) still remains elusive. By PCR-based cloning techniques using soybeans, we have made a successful attempt to clone a delta-subunit homologue of CCT (CCTdelta). This subunit is responsible for the binding of an in vivo substrate, alpha-actin, by assisting the correct folding of the cytoskeletal protein in mouse, and the occurrence of the subunit homologue in plant CCT was unclear. As the cloning strategy, a putative amino acid segment, NH(2)-Gly-Gly-Gly-Ala-Pro-Glu-COOH, which is tightly conserved in all known animal and yeast CCTdelta subunits, was chosen for designing a degenerate primer of the PCR-cloning. The resultant 1881-bp cDNA was found to have an open-reading frame of 533 amino acids with a calculated molecular mass of 57,677 Da and to share about 58-65% identity overall at the amino acid level with the corresponding subunits known to date. Using antibodies raised against Escherichia coli-produced soybean insoluble CCTdelta as a monitoring tool, we purified soybean CCT from the extract of its immature seeds. STEM images demonstrated that the molecular shape of soybean CCT is a double eight-membered ring, which resembles the known group II chaperonins. The CCT also reactivated a denatured firefly luciferase with a significant, but limited level of the native enzymic activity in an in vitro system. Northern blot analysis showed that soybean CCTdelta gene, which is intronless and composed of a small family, was only expressed at a very early stage of seed development of soybean. 相似文献