排序方式: 共有114条查询结果,搜索用时 15 毫秒
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Yim SK Yun CH Ahn T Jung HC Pan JG 《Journal of biochemistry and molecular biology》2005,38(3):366-369
NADPH-cytochrome P450 reductase (CPR) transfers electrons from NADPH to cytochrome P450 and also catalyzes the one-electron reduction of many drugs and foreign compounds. Various spectrophotometric assays have been performed to examine electron-accepting properties of CPR and its ability to reduce cytochrome b5, cytochrome c, and ferricyanide. In this report, reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) by CPR has been assessed as a method for monitoring CPR activity. The principle advantage of this substance is that the reduction of MTT can be assayed directly in the reaction medium by a continuous spectrophotometric method. The electrons released from NADPH by CPR were transferred to MTT. MTT reduction activity was then assessed spectrophotometrically by measuring the increase of A610. MTT reduction followed classical Michaelis-Menten kinetics (K(m)= 20 microM, k(cat)= 1,910 min(-1)). This method offers the advantages of a commercially available substrate and short analysis time by a simple measurement of enzymatic activity of CPR. 相似文献
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The effect of nonlamellar-prone lipids, diacylglycerol (DG) and phosphatidylethanolamine (PE), on the stability of human cytochrome P450 1A2 (CYP1A2) was examined. When 100% phosphatidylcholine (PC) in standard vesicles was gradually replaced with either DG or PE, the stability of CYP1A2 increased; the incubation time-dependent destruction of spectrally detectable P450, decrease of catalytic activity, reduction of intrinsic fluorescence, and increased sensitivity to trypsin digestion were significantly alleviated. The ternary system of PC/PE/DG increased the stability of CYP1A2 more, even at lower concentrations of each nonlamellar-prone lipid, than that of the binary lipid mixture (PC/nonlamellar lipid). By incorporating the nonlamellar-prone lipids, the CYP1A2-induced increase of the surface pressure of the lipid monolayer was much higher compared to that for 100% PC. Increased surface pressure indicates a deep insertion of the protein into lipid monolayers. Nonlamellar lipids also increased the transition temperature of CYP1A2 in thermal unfolding and reduced the incubation time-dependent detachment of membrane-bound CYP1A2 from vesicles. Taken together, these results suggest that nonlamellar lipids per se and/or the phase properties of the membrane containing these lipids are important in the enhanced stability of CYP1A2 and the concomitant maintenance of catalytic activity of the protein. 相似文献
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Park KJ Lee CH Kim A Jeong KJ Kim CH Kim YS 《The Journal of biological chemistry》2012,287(5):3313-3325
Stimulation of the proapoptotic tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptors, death receptors 4 (DR4) and 5 (DR5), conventionally induces caspase-dependent apoptosis in tumor cells. Here we report that stimulation of DR4 and/or DR5 by the agonistic protein KD548-Fc, an Fc-fused DR4/DR5 dual-specific Kringle domain variant, activates plasma membrane-associated Nox1 NADPH oxidase to generate superoxide anion and subsequently accumulates intracellular reactive oxygen species (ROS), leading to sustained c-Jun N-terminal kinase activation and eventual apoptotic cell death in human HeLa and Jurkat tumor cells. KD548-Fc treatment induces the formation of a DR4/DR5 signaling complex containing riboflavin kinase (RFK), Nox1, the Nox1 subunits (Rac1, Noxo1, and Noxa1), TNF receptor-associated death domain (TRADD), and TNF receptor-associated factor 2 (TRAF2). Depletion of RFK, but not the Nox1 subunits, TRADD and TRAF2, failed to recruit Nox1 and Rac1 to DR4 and DR5, demonstrating that RFK plays an essential role in linking DR4/DR5 with Nox1. Knockdown studies also reveal that RFK, TRADD, and TRAF2 play critical, intermediate, and negligible roles, respectively, in the KD548-Fc-mediated ROS accumulation and downstream signaling. Binding assays using recombinantly expressed proteins suggest that DR4/DR5 directly interact with cytosolic RFK through RFK-binding regions within the intracellular death domains, and TRADD stabilizes the DR4/DR5-RFK complex. Our results suggest that DR4 and DR5 have a capability to activate Nox1 by recruiting RFK, resulting in ROS-mediated apoptotic cell death in tumor cells. 相似文献
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Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1) is induced by nonsteroidal anti-inflammatory drugs and possesses proapoptotic and antitumorigenic activities. Although tolfenamic acid (TA) induces apoptosis in head and neck cancer cells, the relationship between NAG-1 and TA has not been determined. This study investigated the induction of apoptosis in head and neck cancer cells treated by TA and the role of NAG-1 expression in this induction. TA reduced head and neck cancer cell viability in a dose-dependent manner and induced apoptosis. The induced apoptosis was coincident with the expression of NAG-1. Overexpression of NAG-1 enhanced the apoptotic effect of TA, whereas suppression of NAG-1 expression by small interfering RNA attenuated TA-induced apoptosis. TA significantly inhibited tumor formation as assessed by xenograft models, and this result accompanied the induction of apoptotic cells and NAG-1 expression in tumor tissue samples. Taken together, these results demonstrate that TA induces apoptosis via NAG-1 expression in head and neck squamous cell carcinoma, providing an additional mechanistic explanation for the apoptotic activity of TA. 相似文献
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Eun-Hee Kim Kwang-Soo Choi Kang-Wook Lee Jun-Gyo Suh Yang-Kyu Choi Byung-Hwa Hyun Akira Ishikawa Takao Namikawa Chul-Ho Lee 《Experimental Animals》2004,53(2):97-102
The FGS/Nga mouse strain, established from an outcross between CBA/N and RFM/Nga mice strains, has previously been reported as a spontaneous mouse model for focal glomerular sclerosis (FGS) and is considered to have two pairs of autosomal recessive genes associated with FGS. In this study, we examined the changes of seven renal lesion-related parameters, blood urea nitrogen (BUN), creatinine, albumin and total protein in plasma, urinary protein, systolic blood pressure, and a glomerulosclerosis index on histological observation, in 20-week-old FGS/Nga mice and their age-matched two parental strains, CBA/N and RFM/Nga. The levels of plasma BUN and creatinine, urinary protein and systolic blood pressure were significantly increased in FGS/Nga, compared with those of the parental strains. RFM/Nga mice showed slightly elevated levels of all biochemical makers. In histological analysis, a higher glomerulosclerosis index was observed in FGS/Nga than the two parental strains. RFM/Nga mice appeared to have slight sclerotic lesions of glomeruli, but no renal failure was observed in CBA/N mice. These results suggest that at least one mutant gene that causes the progression of renal lesion in FGS/Nga mice is derived from RFM/Nga. 相似文献
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Previously, it was found that Ca2+ stimulates the intrinsic Escherichia coli SecA ATPase activity [Kim et al., FEBS Lett. 493 (2001) 12-16]. Now, we suggest that Ca2+ is required for efficient interaction of SecA with membranes and the signal peptide of ribose-binding protein. When the amount of external Ca2+ was enhanced, the amounts of membrane-bound SecA and its lipid/ATPase activity increased. In the presence of entrapped Ca2+ in liposomes, the binding was also stimulated in a Ca2+ concentration-dependent manner. The effect of Ca2+ on the functional regulation of SecA was also evident in the presence of the signal peptides of secretory proteins, which the interaction of SecA with the signal peptide increased with increasing Ca2+ concentration in the presence of membranes. However, other divalent cations including Mg2+, Mn2+, and Zn2+ had inhibitory or no effect, suggesting a specific role of Ca2+ in SecA interaction with lipid bilayers and signal peptides. 相似文献
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Jeong TS Kim EE Lee CH Oh JH Moon SS Lee WS Oh GT Lee S Bok SH 《Bioorganic & medicinal chemistry letters》2003,13(16):2663-2665
Hesperetin ester and ether derivatives possessing a long alkyl chain were synthesized for examining their hypocholesterolemic activities in high cholesterol-fed mice. Hesperetin 7-O-lauryl ether (4b) and hesperetin 7-O-oleyl ether (4e) exhibited strong cholesterol-lowering effects. 相似文献