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61.
Wada K Tada T Nakamura Y Ishikawa T Yabuta Y Yoshimura K Shigeoka S Nishimura K 《Journal of biochemistry》2003,134(2):239-244
Ascorbate peroxidase (APX) is a heme-containing protein that plays a central role in scavenging H(2)O(2) in higher plants. The structure of stromal APX (sAPX) was determined at 1.6 A to an R-factor of 19.1% and an R-free-factor of 22.3%. The electrostatic potential of the gamma-channel that connects the molecular surface of sAPX to the gamma-edge of heme was more positive than that of cytosolic APX (cAPX) from pea, so sAPX might bind more easily with ascorbate than cAPX. The overall structure of sAPX was similar to those of cAPX from pea and cytochrome c peroxidase (CCP) from yeast, with a substantial difference in a loop structure located in the vicinity of the heme. The side chain of Arg169 in sAPX corresponding to His169 in cAPX and His181 in CCP extended in the opposite direction from the heme, forming two hydrogen bonds with carbonyl groups in the loop structure. The rapid inactivation of sAPX might be due to the characteristic conformation of Arg169 owing to the loop structure of sAPX. 相似文献
62.
Up-regulation of sodium-dependent glucose transporter by interaction with heat shock protein 70 总被引:1,自引:0,他引:1
Heat shock stress induces some heat shock proteins, including Hsp70, and activates sodium-dependent glucose transport in porcine renal LLC-PK(1) cells, but its mechanisms have not been described in detail. We investigated whether sodium-dependent glucose transporter (SGLT1) interacts with Hsp70 to increase SGLT1 activity. Heat shock stress increased SGLT1 activity without changing SGLT1 expression. The increase of SGLT1 activity was completely inhibited by an anti-transforming growth factor-beta1 (TGF-beta1) antibody. Instead of heat shock stress, TGF-beta1 increased SGLT1 activity dose- and time-dependently without changing SGLT1 expression. We found that the amount of Hsp70 immunoprecipitated from TGF-beta1-treated cells with an anti-SGLT1 antibody was higher than that of the control cells. Transfection of an anti-Hsp70 antibody into the cells inhibited the increase of SGLT1 activity. With confocal laser microscopy, both SGLT1 and Hsp70 was localized near the apical membrane in the TGF-beta1-treated cells, and an anti-Hsp70 antibody disturbed this localization. Furthermore, we clarified that an anti-Hsp70 antibody inhibited interaction of SGLT1 with Hsp70 in vitro. These results suggest that Hsp70 forms a complex with SGLT1 and increases the expression level of SGLT1 in the apical membrane, resulting in up-regulation of glucose uptake. 相似文献
63.
Fluorescence in situ hybridization has shown that cells labeled with an Archaea-specific probe (ARCH915) accounted for approximately 10% of the total cell count in oil-contaminated groundwater accumulated at the bottom of an underground crude oil storage cavity. Although chemical analyses have revealed vigorous consumption of nitrate in cavity groundwater, the present study found that the methane production rate was higher than the nitrate consumption rate. To characterize the likely archaeal populations responsible for methane production in this system, fragments of 16S ribosomal DNA (rDNA) were amplified by PCR using eight different combinations of universal and Archaea-specific primers. Sequence analysis of 324 clones produced 23 different archaeal sequence types, all of which were affiliated with the kingdom EURYARCHAEOTA: Among them, five sequence types (KuA1, KuA6, KuA12, KuA16, and KuA22) were obtained in abundance. KuA1 and KuA6 were closely related to the known methanogens Methanosaeta concilii (99% identical) and Methanomethylovorans hollandica (98%), respectively. Although no closely related organism was found for KuA12, it could be affiliated with the family METHANOMICROBIACEAE: KuA16 and KuA22 showed substantial homology only to some environmental clones. Both of these branched deeply in the Euryarchaeota, and may represent novel orders. Quantitative competitive PCR showed that KuA12 was the most abundant, accounting for approximately 50% of the total archaeal rDNA copies detected. KuA1 and KuA16 also constituted significant proportions of the total archaeal rDNA copies (7 and 17%, respectively). These results suggest that limited species of novel archaea were enriched in the oil storage cavity. An estimate of specific methane production rates suggests that they were active methanogens. 相似文献
64.
A bacterial consortium which rapidly mineralizes benzo[a]pyrene when it is grown on a high-boiling-point diesel fuel distillate (HBD) was recovered from soil and maintained for approximately 3 years. Previous studies have shown that mobilization of benzo[a]pyrene into the supernatant liquid precedes mineralization of this compound (R. Kanaly, R. Bartha, K. Watanabe, and S. Harayama, Appl. Environ. Microbiol. 66:4205-4211, 2000). In the present study, we found that sterilized supernatant liquid filtrate (SSLF) obtained from the growing consortium stimulated mineralization of benzo[a]pyrene when it was readministered to a consortium inoculum without HBD. Following this observation, eight bacterial strains were isolated from the consortium, and SSLF of each of them was assayed for the ability to stimulate benzo[a]pyrene mineralization by the original consortium. The SSLF obtained from one strain, designated BPC1, most vigorously stimulated benzo[a]pyrene mineralization by the original consortium; its effect was more than twofold greater than the effect of the SSLF obtained from the original consortium. A 16S rRNA gene sequence analysis and biochemical tests identified strain BPC1 as a member of the genus Rhodanobacter, whose type strain, Rhodanobacter lindaniclasticus RP5557, which was isolated for its ability to grow on the pesticide lindane, is not extant. Strain BPC1 could not grow on lindane, benzo[a]pyrene, simple hydrocarbons, and HBD in pure culture. In contrast, a competitive PCR assay indicated that strain BPC1 grew in the consortium fed only HBD and benzo[a]pyrene. This growth of BPC1 was concomitant with growth of the total bacterial consortium and preceded the initiation of benzo[a]pyrene mineralization. These results suggest that strain BPC1 has a specialized niche in the benzo[a]pyrene-mineralizing consortium; namely, it grows on metabolites produced by fellow members and contributes to benzo[a]pyrene mineralization by increasing the bioavailability of this compound. 相似文献
65.
Effect of taurine on cholesterol metabolism in hamsters: up-regulation of low density lipoprotein (LDL) receptor by taurine 总被引:2,自引:0,他引:2
The effects of taurine on hepatic cholesterol metabolism were investigated in hamsters fed a high-fat diet or normal chow. Two weeks-treatment of taurine at 1% in drinking water prevented high-fat diet-induced increase in cholesterol levels of serum and liver. The decrease in serum cholesterol by taurine was due to decrease in non-HDL cholesterols. A similar tendency was noted in serum and liver cholesterol levels of hamsters fed a normal diet. In hamsters fed a high-fat diet, taurine prevented elevation in hepatic activity of acyl-CoA:cholesterol acyltransferase (ACAT) and increased the activity of cholesterol 7alpha-hydroxylase. Taurine also increased cholesterol 7alpha-hydroxylase activity in hamsters fed normal chow. Studies on liver membranes revealed that taurine increased 125I-labeled LDL binding by 52% and 58% in hamsters fed either a normal chow or high-fat diet, respectively. Furthermore, LDL kinetic analysis showed that taurine intake resulted in significant faster plasma LDL fractional catabolic rates (FCR). These results suggest that taurine elevates hepatic LDL receptor and thereby decreases serum cholesterol levels, an event which may be the result of hepatic cholesterol depletion as a consequence of increased bile acid synthesis via enhancement of cholesterol 7alpha-hydroxylase activity. Thus, up-regulation of the LDL receptor and subsequent increase in receptor- mediated LDL turnover may be a key event in the cholesterol-lowering effects of taurine in hamsters. 相似文献
66.
Kobayashi N Takahashi K Takayanagi K Takahashi K Masuko S Tadano T Kisara K Kinemuchi H 《Life sciences》2002,70(13):1519-1531
Various mammalian tissues contain a tissue-bound amine oxidizing enzyme distinct from mitochondrial outer membrane enzyme, monoamine oxidase (MAO, EC 1.4.3.4), termed semicarbazide-sensitive amine oxidase (SSAO, EC 1.4.3.6). An increase in SSAO activity was found in patients suffering from vascular disorders such as diabetes and diabetic complications. It has previously been shown that 2-bromoethylamine (2-BEA) is a potent, and selective suicidal inhibitor of tissue-bound SSAO. The aim of this study was to investigate the interaction of this suicidal SSAO inhibitor with the tissue-bound enzyme in guinea pig lung, kidney, stomach, and heart homogenates. The conditions necessary for this inhibitor to titrate the concentrations of this enzyme were also determined. 2-BEA appears to interact with SSAO, as reported previously for this enzyme from different sources, in a manner consistent with an irreversible, "suicide" reaction. Because of this property, 2-BEA could be used to titrate the concentrations of SSAO active centers in these tissues under the appropriate conditions employed. Although some possible non-specific binding of the inhibitor to sites other than the active center of the enzyme, metabolism of this inhibitor and/or presence of enzyme subtypes was hypothesized, the molecular characteristics of SSAO in these tissues (Km, Vmax values, enzyme efficiencies, approximate enzyme concentrations, and molecular turnover numbers) towards the substrate kynuramine (0.1 mM) at pH 7.4 and 37 degrees C have been estimated. 相似文献
67.
Seko T Kato M Kohno H Ono S Hashimura K Takenobu Y Takimizu H Nakai K Maegawa H Katsube N Toda M 《Bioorganic & medicinal chemistry letters》2002,12(17):2267-2269
This study was performed to determine the structure-activity relationships (SAR) of L-cysteine based N-type calcium channel blockers. Basic nitrogen was introduced into the C-terminal lipophilic moiety of L-cysteine with a view toward improvement of its physicochemical properties. L-Cysteine derivative 9 was found to be a potent and selective N-type calcium channel blocker with IC(50) of 0.33 microM in calcium influx assay using IMR-32 cells and was 15-fold selective for N-type calcium channels over L-type channels. Compound 9 showed improved oral analgesic efficacy in the rat formalin induced pain model and the rat chronic constriction injury (CCI) model, which is one of the most reliable models of chronic neuropathic pain, without any significant effect on blood pressure or neurological behavior. 相似文献
68.
Yoshiizumi K Nakajima F Dobashi R Nishimura N Ikeda S 《Bioorganic & medicinal chemistry》2002,10(8):2445-2460
Scavenger receptors have been proven to be implicated in the formation of atherosclerotic lesions. A series of novel derivatives of sulfatides were synthesized, and their inhibitory activities against incorporation of DiI-acetyl-LDL into macrophages were evaluated in order to clarify the structure-activity relationships of sulfatides as a scavenger receptor inhibitor and find out novel inhibitors with synthetic easiness. The chemical modification of the substructures of sulfatides led to the establishment of the following structure-activity relationships; (1) the ceramide moiety can be replaced with another structure bearing two long chains, (2) the galactose moiety can be replaced with another structure or be deleted without a large decrease in the inhibitory activity, (3) the sulfate moiety was crucial, and it was the most preferable functional group for a potent inhibitory activity. The inhibitory activity of (S)-2-octadecanoylamino-2-tetradecylcarbamoyl)ethyl sulfate sodium salt (3a) against incorporation of DiI-acetyl-LDL into macrophages was proven to be based on the inhibition against the binding of acetyl-LDL to the surface of macrophages. We discovered novel scavenger receptor inhibitors with synthetic easiness, such as (S)-2-octadecanoylamino-2-(tetradecylcarbamoyl)ethyl sulfate sodium salt (3a) and 2-octadecanoylamino-1-(octadecanoylaminomethyl)ethyl sulfate sodium salt (13q). 相似文献
69.
Deligeer Fukunaga R Kataoka K Yamaguchi K Kobayashi K Tagawa S Suzuki S 《Journal of inorganic biochemistry》2002,91(1):132-138
The Cu-containing nitrite reductase from Hyphomicrobium denitrificans (HydNIR) has been spectroscopically and functionally characterized. The visible absorption spectrum implies that the enzyme has two type 1 Cu ions in one subunit (ca. 50 kDa). The electron paramagnetic resonance (EPR) spectrum of HydNIR is simulated assuming the sum of three distinct S = 1/2 systems: two type 1 Cu signals (axial and rhombic symmetries) and one type 2 Cu signal. The intramolecular electron transfer reaction from the type 1 Cu to the type 2 Cu at pH 6.0 does not occur in the absence of nitrite, but a very slow electron transfer reaction is observed in the presence of nitrite. The apparent first-order rate constants for the intramolecular electron transfer reactions (k(ET(intra))) in the presence of nitrite and also the apparent catalytic rate constants (k(cat)) of HydNIR decrease gradually with increasing pH in the range of pH 4.5-7.5. These pH profiles are substantially similar to each other, suggesting that the intramolecular electron transfer process is linked to the subsequent nitrite reduction process. 相似文献
70.
Asexual worms of an exclusively fissiparous strain (the OH strain) of the planarian Dugesia ryukyuensis keep developing hermaphroditic reproductive organs and eventually undergo sexual reproduction instead of asexual reproduction, namely fission, if they are fed with sexually mature worms of an exclusively oviparous planarian, Bdellocephala brunnea, suggesting that the sexually mature worms has a sexualizing substance(s). The fully sexualized worms no longer need the feeding on sexual worms to maintain the sexuality. Here, we demonstrate that the sexualized worms produce enough of their own sexualizing substance similar to that contained in B. brunnea. In case of surgical ablation of the sexualized worms, the fragments with sexual organs regenerate to become sexual, while those without sexual organs, namely head fragments, regenerate to return to the asexual state. The asexual regenerants from the sexualized worms are also fully sexualized by being fed with B. brunnea. Additionally, it was reported that head region in sexually mature worms lacks the putative sexualizing substance necessary for complete sexualization (Sakurai, 1981). These results suggest that the fragments without sexual organ lack enough of an amount of the putative sexualizing substance and the sexuality is maintained by the sexualizing substance contained in the sexualized worms. 相似文献