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1.
Involvement of the Binuclear Copper Site in the Proteolytic Activity of Polyphenol Oxidase 总被引:2,自引:0,他引:2
Plant polyphenol oxidase (PPO) is apt to degrade during andeven after purification. We developed a method to stabilizePPO by 0.3 M NaCl, 0.1% (w/v) Tween 20, and 50% (w/v) ethyleneglycol at pH 6.5. The protein slowly degraded by itself whenthe stabilizing reagents were removed. Ascorbate and/or H2O2accelerated the degradation. The ascorbate-induced degradationwas inhibited by catalase, suggesting that H2O2 is generatedthrough reduction of PPO by ascorbate. It is likely that dissolvedoxygen is converted to peroxide through two-electron reductionby the reaction center of PPO, binuclear Cu site, and a Fenton-typereaction occurred on it. This understanding was supported bythe finding that the H2O2-induced degradation was inhibitedby metal-chelators as well as by polyphenolic substrate of PPO.Considering the postulated mechanism of the self-degradationof PPO, we re-examined the degradation of the 23-kDa proteinof PSII by PPO [Kuwabara et al. (1997) Plant Cell Physiol. 38:179]. The obtained results suggested that the 23-kDa proteintriggers the active oxygen production by the binuclear Cu site,probably as reductant, and receives the radical species preferentiallyto the polypeptide moiety of PPO. (Received April 15, 1999; Accepted July 21, 1999) 相似文献
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Tomohiko J. Itoh Hidemi Sato 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,800(1):21-27
The initial rate and final extent of polymerization of both bovine brain tubulin and sea urchin egg tubulin were enhanced in the presence of 2H2O. The yields were increased in association with the elevation of the 2H2O concentration. 2H2O also reduced the critical concentration for polymerization of brain tubulin. Thermodynamic analysis was attempted using the temperature dependence of the critical concentration for polymerization in the presence of 2H2O. We obtained linear van 't Hoff plots and calculated thermodynamic parameters which were positive and were increased with the elevation of the 2H2O concentration. The enhancement of the polymerization of tubulin by 2H2O could, therefore, be the result of the strenghening of intra-and/or inter-molecular hydrophobic interactions of the tubulin molecules. We believe that the increase in lenghth and number of microtubules of the mitotic spindles in the dividing cells of the eukaryotes with 2H2O may be caused by the direct involvement of 2H2O in the polymerization of tubulin. 相似文献
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Yosuke?Shida Kaori?Yamaguchi Mikiko?Nitta Ayana?Nakamura Machiko?Takahashi Shun-ichi?Kidokoro Kazuki?Mori Kosuke?Tashiro Satoru?Kuhara Tomohiko?Matsuzawa Katsuro?Yaoi Yasumitsu?Sakamoto Nobutada?Tanaka Yasushi?Morikawa Wataru?OgasawaraEmail author 《Biotechnology for biofuels》2015,8(1):230
Background
The filamentous fungus Trichoderma reesei (anamorph of Hypocrea jecorina) produces increased cellulase expression when grown on cellulose or its derivatives as a sole carbon source. It has been believed that β-glucosidases of T. reesei not only metabolize cellobiose but also contribute in the production of inducers of cellulase gene expression by their transglycosylation activity. The cellulase hyper-producing mutant PC-3-7 developed in Japan has enhanced cellulase production ability when cellobiose is used as the inducer. The comparative genomics analysis of PC-3-7 and its parent revealed a single-nucleotide mutation within the bgl2 gene encoding intracellular β-glucosidase II (BGLII/Cel1a), giving rise to an amino acid substitution in PC-3-7, which could potentially account for the enhanced cellulase expression when these strains are cultivated on cellulose and cellobiose.Results
To analyze the effects of the BGLII mutation in cellulase induction, we constructed both a bgl2 revertant and a disruptant. Enzymatic analysis of the transformant lysates showed that the strain expressing mutant BGLII exhibited weakened cellobiose hydrolytic activity, but produced some transglycosylation products, suggesting that the SNP in bgl2 strongly diminished cellobiase activity, but did not result in complete loss of function of BGLII. The analysis of the recombinant BGLII revealed that transglycosylation products might be oligosaccharides, composed probably of glucose linked β-1,4, β-1,3, or a mixture of both. PC-3-7 revertants of bgl2 exhibited reduced expression and inducibility of cellulase during growth on cellulose and cellobiose substrates. Furthermore, the effect of this bgl2 mutation was reproduced in the common strain QM9414 in which the transformants showed cellulase production comparable to that of PC-3-7.Conclusion
We conclude that BGLII plays an important role in cellulase induction in T. reesei and that the bgl2 mutation in PC-3-7 brought about enhanced cellulase expression on cellobiose. The results of the investigation using PC-3-7 suggested that other mutation(s) in PC-3-7 could also contribute to cellulase induction. Further investigation is essential to unravel the mechanism responsible for cellulase induction in T. reesei.7.
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Ryutaro Kakinuma Noriyuki Moriyama Yukio Muramatsu Shiho Gomi Masahiro Suzuki Hirobumi Nagasawa Masahiko Kusumoto Tomohiko Aso Yoshihisa Muramatsu Takaaki Tsuchida Koji Tsuta Akiko Miyagi Maeshima Naobumi Tochigi Shun-ichi Watanabe Naoki Sugihara Shinsuke Tsukagoshi Yasuo Saito Masahiro Kazama Kazuto Ashizawa Kazuo Awai Osamu Honda Hiroyuki Ishikawa Naoya Koizumi Daisuke Komoto Hiroshi Moriya Seitaro Oda Yasuji Oshiro Masahiro Yanagawa Noriyuki Tomiyama Hisao Asamura 《PloS one》2015,10(12)
9.
Po-sung Chu Hirotoshi Ebinuma Nobuhiro Nakamoto Kazuo Sugiyama Shingo Usui Yuko Wakayama Nobuhito Taniki Akihiro Yamaguchi Shunsuke Shiba Yoshiyuki Yamagishi Takaji Wakita Toshifumi Hibi Hidetsugu Saito Takanori Kanai 《PloS one》2015,10(5)
Hepatitis C virus (HCV) genotype 1 infections are significantly more difficult to eradicate with PEG-IFN/ribavirin therapy, compared to HCV genotype 2. The aim of this work is to investigate the difference of immunological impairments underlying this phenomenon. Pre-treatment NKG2D expression on peripheral CD56+CD3+ lymphocytes and CD56+CD3− NK cells from cases of chronic hepatitis C were analyzed and assessed by treatment effect. Two strains of HCV were used to co-incubate with immune cells in vitro. NKG2D expression on peripheral CD56+CD3+ lymphocytes, but not NK cells, was significantly impaired in genotype 1 infection, compared to genotype 2. When peripheral blood mononuclear cells from healthy donors were co-incubated with TNS2J1, a genotype 1b/2a chimera strain, or with JFH1, a genotype 2a strain, genotype-specific decrease of NKG2D on CD56+CD3+ lymphocytes, but not NK cells, was observed. Pre-treatment NKG2D expression on peripheral CD56+CD3+ lymphocytes significantly correlated with reduction in serum HCV RNA levels from week 0 to week 4, and predicted treatment response. Ex vivo stimulation of peripheral CD56+CD3+ lymphocytes showed NKG2D expression-correlated IFN-γ production. In conclusion, Decreased NKG2D expression on CD56+CD3+ lymphocytes in chronic HCV genotype 1 infection predicts inferior treatment response to PEG-IFN/ribavirin therapy compared to genotype 2. 相似文献
10.
Satoi Nagasawa Anna S. Sedukhina Yuko Nakagawa Ichiro Maeda Manabu Kubota Shigeko Ohnuma Koichiro Tsugawa Tomohiko Ohta Marta Roche-Molina Juan A. Bernal Ana J. Narváez Anand D. Jeyasekharan Ko Sato 《PloS one》2015,10(2)
LSD1, a lysine-specific histone demethylase, is overexpressed in several types of cancers and linked to poor outcomes. In breast cancer, the significance of LSD1 overexpression is not clear. We have performed an in silico analysis to assess the relationship of LSD1 expression to clinical outcome. We demonstrate that LSD1 overexpression is a poor prognostic factor in breast cancer, especially in basal-like breast cancer, a subtype of breast cancer with aggressive clinical features. This link is also observed in samples of triple negative breast cancer. Interestingly, we note that overexpression of LSD1 correlates with down-regulation of BRCA1 in triple negative breast cancer. This phenomenon is also observed in in vitro models of basal-like breast cancer, and is associated with an increased sensitivity to PARP inhibitors. We propose therefore that high expression levels of the demethylase LSD1 is a potential prognostic factor of poor outcome in basal-like breast cancer, and that PARP inhibition may be a therapeutic strategy of interest in this poor prognostic subtype with overexpression of LSD1. 相似文献