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101.
Enzymatic synthesis of arbutin undecylenic acid ester and its inhibitory effect on mushroom tyrosinase 总被引:1,自引:0,他引:1
A novel tyrosinase inhibitor, an arbutin derivative having undecylenic acid at the 6-position of its glucose moiety, was enzymatically
synthesized. Its inhibitory activity was studied in vitro by using catechol and phenol as substrates. The IC50 value of the arbutin ester on tyrosinase using catechol (4 × 10−4 M) was 1% of that when arbutin (4 × 10−2 M) was used. Using phenol, IC50 of the arbutin ester (3 × 10−4 M) as substrate was 10% of that of arbutin (3 × 10−3 M). These results suggest that the arbutin ester inhibits the latter part of the tyrosinase reaction, which consists of hydroxylation
and oxidation. 相似文献
102.
Adaptor proteins Grb2 and Crk couple Pyk2 with activation of specific mitogen-activated protein kinase cascades. 总被引:9,自引:0,他引:9
A Blaukat I Ivankovic-Dikic E Gr?nroos F Dolfi G Tokiwa K Vuori I Dikic 《The Journal of biological chemistry》1999,274(21):14893-14901
The protein tyrosine kinase Pyk2 acts as an upstream regulator of mitogen-activated protein (MAP) kinase cascades in response to numerous extracellular signals. The precise molecular mechanisms by which Pyk2 activates distinct MAP kinase pathways are not yet fully understood. In this report, we provide evidence that the protein tyrosine kinase Src and adaptor proteins Grb2, Crk, and p130Cas act as downstream mediators of Pyk2 leading to the activation of extracellular signal-regulated kinase (ERK) and c-Jun amino-terminal kinase (JNK). Pyk2-induced activation of Src is necessary for phosphorylation of Shc and p130Cas and their association with Grb2 and Crk, respectively, and for the activation of ERK and JNK cascades. Expression of a Grb2 mutant with a deletion of the amino-terminal Src homology 3 domain or the carboxyl-terminal tail of Sos strongly reduced Pyk2-induced ERK activation, with no apparent effect on JNK activity. Grb2 with a deleted carboxyl-terminal Src homology 3 domain partially blocked Pyk2-induced ERK and JNK pathways, whereas expression of dominant interfering mutants of p130Cas or Crk specifically inhibited JNK but not ERK activation by Pyk2. Taken together, our data reveal specific pathways that couple Pyk2 with MAP kinases: the Grb2/Sos complex connects Pyk2 to the activation of ERK, whereas adaptor proteins p130Cas and Crk link Pyk2 with the JNK pathway. 相似文献
103.
104.
A modified method for isolating poly(vinyl alcohol)-degrading bacteria and study of their degradation patterns 总被引:5,自引:0,他引:5
An addition of catalase or peroxidase into an agar plate containing poly(vinyl alcohol) (PVA), was effective for the isolation of PVA-degrading microorganisms. A Gram-negative bacterium, strain TK-2 (-group of proteobacteria), rapidly degraded a high molecular weight PVA to low molecular weight material after 1 day thereby producing oligomers of PVA as shown by gel permeation chromatography. Conversely, Sphingomonas strain TJ-7 did not produce any PVA oligomers, suggesting that the strain TJ-7 degraded PVA from the terminal ends of the molecules, whereas the strain TK-2 cleaved PVA at random. 相似文献
105.
Masaru Kitagawa Tomoo Tokiwa Hong Fan Takao Raku Yutaka Tokiwa 《Biotechnology letters》2000,22(10):879-882
The transesterification of 1 M divinyladipate with 0.25 M glucose in dimethylformamide (DMF) catalyzed by 5 mg ml–1 alkaline protease (24 units mg–1 min–1) from Streptomyces sp. gave 6-O-vinyladipoyl d-glucose as the main product with yields are between 60 and 90%. The optimum temperature for the reaction was about 50 °C. 相似文献
106.
The rec-assay of the nitropyrenes in Bacillus subtilis was performed. All nitropyrene derivatives were positive in this system. Especially, 3 isomers of 1,3-, 1,6- and 1,8-dinitropyrene and 4-nitropyrene were found to possess strong DNA-damaging capacities at extremely low concentrations. 相似文献
107.
The transesterification of divinylsebacate with glucose in pyridine was catalyzed by Alcaligenes sp. lipase at more than 99% of conversion rate. The sugar ester could be polymerized in dimethylformamide with 2,2'-azobis(isobutyronitrile) to give the new branched polymer, poly (6-O-vinylsebacyl-D-glucose), having molecular weight (Mn) of 11,000. © Rapid Science Ltd. 1998 相似文献
108.
Yuka Nakano Yasuo Watanabe Yoshihiko Ito Shizuo Yamada Hiroaki Tokiwa 《Bioinformation》2012,8(25):1245-1248
We propose a theoretical novel homodimer model of the β- adrenergic
receptor (βAR) in complex with a heterogeneous mixture of free fatty
acids (FFAs) and cholesterol based on first-principles calculations. We used the
density-functional-based tight binding with dispersion (DFTB-D) method, which
accurately evaluates van der Waals interactions between FFAs and amino acid
residues in the receptor. The calculations suggest that a stable homodimer of
bAR can form a complex with FFAs and cholesterol by extensive van der Waals
interactions in the cell membrane, and that the heterogeneous composition of the
FFAs is important for the stability of the homodimer complex. The stable van der
Waals interactions propagate from one of the bAR to the other through the
cholesterol and FFAs in the homodimer complex. The energy propagation in the
complex has the potential to enhance molecular signaling in adipocytes, because
the stability of the complex can influence anti-adiposity effects after oral
treatment of the FFA components. 相似文献
109.
Uchida Y Osaki T Yamasaki T Shimomura T Hata S Horikawa K Shibata S Todo T Hirayama J Nishina H 《The Journal of biological chemistry》2012,287(11):8318-8326
The stress kinase mitogen-activated protein kinase kinase 7 (MKK7) is a specific activator of c-Jun N-terminal kinase (JNK), which controls various physiological processes, such as cell proliferation, apoptosis, differentiation, and migration. Here we show that genetic inactivation of MKK7 resulted in an extended period of oscillation in circadian gene expression in mouse embryonic fibroblasts. Exogenous expression in cultured mammalian cells of an MKK7-JNK fusion protein that functions as a constitutively active form of JNK induced phosphorylation of PER2, an essential circadian component. Furthermore, JNK interacted with PER2 at both the exogenous and endogenous levels, and MKK7-mediated JNK activation increased the half-life of PER2 protein by inhibiting its ubiquitination. Notably, the PER2 protein stabilization induced by MKK7-JNK fusion protein reduced the degradation of PER2 induced by casein kinase 1ε. Taken together, our results support a novel function for the stress kinase MKK7 as a regulator of the circadian clock in mammalian cells at steady state. 相似文献
110.
Yung-Hun Yang Takao Raku Eunjung Song Sung-Hee Park Dongwon Yoo Hyung-Yeon Park Byung-Gee Kim Hyung-Ju Kim Sang-Hyun Lee Hyung-Sup Kim Yutaka Tokiwa 《Biotechnology and Bioprocess Engineering》2012,17(1):50-54
To perform the lipase-catalyzed synthesis of L-ascorbic acid derivatives from plant-based compounds such as cinnamic and ferulic acid under mild reaction conditions, the activities of immobilized Candida ntarctica lipase with different cinnamic acid esters and substituted cinnamic acids were compared. As a result, immobilized C. ntarctica lipase was found to prefer vinyl cinnamic acid to other esters such as allyl-, ethyl-, and isobutyl cinnamic acids as well as substituted cinnamic acids such as p-coumaric acid, caffeic acid, ferulic acid, and sinapic acid. Based on these results, large-scale synthesis of 6-O-cinnamyl-L-ascorbic acid ester was performed using immobilized C. ntarctica lipase in dry organic solvent, resulting in 68% yield (493 mg) as confirmed by 13C-NMR. 相似文献