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91.
Nakano C Motegi A Sato T Onodera M Hoshino T 《Bioscience, biotechnology, and biochemistry》2007,71(10):2543-2550
Sterol biosynthesis by prokaryotic organisms is very rare. Squalene epoxidase and lanosterol synthase are prerequisite to cyclic sterol biosynthesis. These two enzymes, from the methanotrophic bacterium Methylococcus capsulatus, were functionally expressed in Escherichia coli. Structural analyses of the enzymatic products indicated that the reactions proceeded in a complete regio- and stereospecific fashion to afford (3S)-2,3-oxidosqualene from squalene and lanosterol from (3S)-2,3-oxidosqualene, in full accordance with those of eukaryotes. However, our result obtained with the putative lanosterol synthase was inconsistent with a previous report that the prokaryote accepts both (3R)- and (3S)-2,3-oxidosqualenes to afford 3-epi-lanosterol and lanosterol, respectively. This is the first report demonstrating the existence of the genes encoding squalene epoxidase and lanosterol synthase in prokaryotes by establishing the enzyme activities. The evolutionary aspect of prokaryotic squalene epoxidase and lanosterol synthase is discussed. 相似文献
92.
Small‐molecule auxin inhibitors that target YUCCA are powerful tools for studying auxin function
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Yusuke Kakei Chiaki Yamazaki Masashi Suzuki Ayako Nakamura Akiko Sato Yosuke Ishida Rie Kikuchi Shouichi Higashi Yumiko Kokudo Takahiro Ishii Kazuo Soeno Yukihisa Shimada 《The Plant journal : for cell and molecular biology》2015,84(4):827-837
Auxin is essential for plant growth and development, this makes it difficult to study the biological function of auxin using auxin‐deficient mutants. Chemical genetics have the potential to overcome this difficulty by temporally reducing the auxin function using inhibitors. Recently, the indole‐3‐pyruvate (IPyA) pathway was suggested to be a major biosynthesis pathway in Arabidopsis thaliana L. for indole‐3‐acetic acid (IAA), the most common member of the auxin family. In this pathway, YUCCA, a flavin‐containing monooxygenase (YUC), catalyzes the last step of conversion from IPyA to IAA. In this study, we screened effective inhibitors, 4‐biphenylboronic acid (BBo) and 4‐phenoxyphenylboronic acid (PPBo), which target YUC. These compounds inhibited the activity of recombinant YUC in vitro, reduced endogenous IAA content, and inhibited primary root elongation and lateral root formation in wild‐type Arabidopsis seedlings. Co‐treatment with IAA reduced the inhibitory effects. Kinetic studies of BBo and PPBo showed that they are competitive inhibitors of the substrate IPyA. Inhibition constants (Ki) of BBo and PPBo were 67 and 56 nm , respectively. In addition, PPBo did not interfere with the auxin response of auxin‐marker genes when it was co‐treated with IAA, suggesting that PPBo is not an inhibitor of auxin sensing or signaling. We propose that these compounds are a class of auxin biosynthesis inhibitors that target YUC. These small molecules are powerful tools for the chemical genetic analysis of auxin function. 相似文献
93.
Nakano C Ootsuka T Takayama K Mitsui T Sato T Hoshino T 《Bioscience, biotechnology, and biochemistry》2011,75(1):75-81
The Rv3377c and Rv3378c genes from Mycobacterium tuberculosis are specifically found in the virulent Mycobacterium species, but not in the avirulent species. The Rv3378c-encoded enzyme produced tuberculosinol 2 (5(6), 13(14)-halimadiene-15-ol), 13R-5a and 13S-isotuberculosinol 5b (5(6), 14(15)-halimadiene-13-ol) as its enzymatic products from tuberculosinyl diphosphate 3, indicating that the Rv3378c enzyme catalyzed the nucleophilic addition of a water molecule after the release of a diphosphate moiety. The three enzymatic products 2, 5a, and 5b were produced irrespective of the N- and C-terminal His-tagged Rv3378c enzymes, and of the maltose-binding protein fusion enzyme; the product distribution ratio was identical between the enzymes as 1:1 for 2:5, and 1:3 for 5a:5b. The successful separation of 5a and 5b by a chiral HPLC column provided the first complete assignments of 1H- and 13C-NMR data for 5a and 5b. The enzymatic mechanism for producing 2, 5a, and 5b is proposed here, and the optimal catalytic conditions and kinetic parameters, in addition to the divalent metal effects, are described. Site-directed mutagenesis of Asp into Asn, targeted at the DDXXD motif, resulted in significantly decreased enzymatic activity. 相似文献
94.
Nishizawa R Nishiyama T Hisaichi K Minamoto C Murota M Takaoka Y Nakai H Tada H Sagawa K Shibayama S Fukushima D Maeda K Mitsuya H 《Bioorganic & medicinal chemistry》2011,19(13):4028-4042
Based on the original spirodiketopiperazine design framework, further optimization of an orally available CCR5 antagonist was undertaken. Structural hybridization of the hydroxylated analog 4 derived from one of the oxidative metabolites and the new orally available non-hydroxylated benzoic acid analog 5 resulted in another potent orally available CCR5 antagonist 6a as a clinical candidate. Full details of a structure-activity relationship (SAR) study and ADME properties are presented. 相似文献
95.
MicroRNA (miR)-17-92a expression plays a crucial role in lymphocyte ontogeny. We therefore set out to determine miR-92a expression levels in peripheral blood lymphocytes from healthy subjects to ascertain any association between these levels and ageing. We found a positive correlation between the miR-92a expression level and the percentages of RO-CD8+CD27+ (P = 0.0046) and CD3+CD8+CD62L+ (P = 0.0011). This suggests that the majority of miR-92a of CD8+ T cells is derived from naïve cells, and the miR-92a expression level in CD8+ T cells declines progressively with age. These results indicate that the age-related attrition of naïve T cells is linked to a reduction of miR-92a in human T -lymphocytes. Therefore, we should careful attention when evaluating human miRNA levels in T lymphocytes to use normal control values. 相似文献
96.
Vissenberg K Oyama M Osato Y Yokoyama R Verbelen JP Nishitani K 《Plant & cell physiology》2005,46(1):192-200
Xyloglucan endotransglucosylase/hydrolases (XTHs) are a class of enzymes that are capable of splitting and reconnecting xyloglucan molecules, and are implicated in the construction and restructuring of the cellulose/xyloglucan framework. Thirty-three members of the XTH gene family are found in the genome of Arabidopsis thaliana, but their roles remain unclear. Here, we describe the tissue-specific and growth stage-dependent expression profiles of promoter::GUS fusion constructs for four Arabidopsis XTH genes, AtXTH17, AtXTH18, AtXTH19 and AtXTH20, which are phylogenetically closely related to one another. AtXTH17 and AtXTH18 were expressed in all cell types in the elongating and differentiating region of the root, while AtXTH19 was expressed in the apical dividing and elongating regions, as well as in the differentiation zone, and was up-regulated by auxin. In contrast, AtXTH20 was expressed specifically in vascular tissues in the basal mature region of the root. This expression analysis also disclosed cis-regulatory sequences that are conserved among the four genes, and are responsible for the root-specific expression profile. These results indicate that the four XTH genes, which were generated by gene duplication, have diversified their expression profile within the root in such a way as to take responsibility for particular physiological roles in the cell wall dynamics. 相似文献
97.
Identification of an allele of VAM3/SYP22 that confers a semi-dwarf phenotype in Arabidopsis thaliana 总被引:1,自引:0,他引:1
Ohtomo I Ueda H Shimada T Nishiyama C Komoto Y Hara-Nishimura I Takahashi T 《Plant & cell physiology》2005,46(8):1358-1365
The short stem and midrib (ssm) mutants of Arabidopsis thaliana show both semi-dwarf and wavy leaf phenotypes due to defects in the elongation of the stem internodes and leaves. Moreover, these abnormalities cannot be recovered by exogenous phytohormones. ssm was originally identified as a single recessive mutant of the ecotype Columbia (Col-0), but genetic crossing experiments have revealed that this mutant phenotype is restored by another gene that is functional in the ecotype Landsberg erecta (Ler) and not in Col-0. Map-based cloning of the gene that is defective in ssm mutants has uncovered a small deletion in the sixth intron of a gene encoding a syntaxin, VAM3/SYP22, which has been implicated in vesicle transport to the vacuole. This mutation appears to cause a peptide insertion in the deduced VAM3/SYP22 polypeptide sequence due to defective splicing of the shortened sixth intron. Significantly, when compared with the wild-type Ler genome, the wild-type Col-0 genome has a single base pair deletion causing a frameshift mutation in SYP23, a gene with the highest known homology to VAM3/SYP22. These findings suggest that VAM3/SYP22 and SYP23 have overlapping functions and that the vesicle transport mediated by these syntaxins is important for shoot morphogenesis. 相似文献
98.
99.
Ishihara K Oyamada C Matsushima R Murata M Muraoka T 《Bioscience, biotechnology, and biochemistry》2005,69(10):1824-1830
Porphyran is a major component of the red algae, Porphyra tenera and P. yezoensis, which are processed into a sheet type of dried food, "Nori". Porphyran has been reported to activate murine macrophages by in vitro and i.p. injection studies. The contact hypersensitivity (CHS) reaction in mice is commonly used as a model to evaluate the anti-allergic activity of food and food components. We therefore studied the effect of porphyran on the CHS reaction in Balb/c mice to evaluate anti-allergic activity of porphyran. We found that an oral administration of porphyran (2% in drinking water) suppressed the CHS reaction (ear edema) induced by 2,4,6-trinitrochlorobenzene. We also found that porphyran suppressed the serum level of IgE and the production of interferon-gamma (IFN-gamma) in the challenged ear lobe. We conclude from these results that the CHS reaction was suppressed by oral porphyran due to the decreased serum level of IgE and the production of IFN-gamma in the challenged ear lobe. 相似文献
100.