Molecular cloning and expression of an isomalto-dextranase gene from Arthrobacter globiformis T6.

The gene encoding an extracellular isomalto-dextranase, designated imd, was isolated from the chromosomal DNA of Arthrobacter globiformis T6 and cloned and expressed in Escherichia coli. A single open reading frame consisting of 1,926 base pairs that encoded a polypeptide composed of a signal peptide of 39 amino acids and a mature protein of 602 amino acids (M(r), 65,900) was found. The primary structure had no significant homology with the structures of any other reported carbohydrases, including two other dextranases. Transformed E. coli cells carrying the 2.3-kb fragment overproduced isomalto-dextranase into the periplasmic space under control of the promoter of the imd gene itself.     

铁棍山药多糖对四氯化碳诱导的急性小鼠肝损伤的保护作用

为了研究铁棍山药(D.oppositacv.Tiegun)多糖对四氯化碳诱导的小鼠急性肝损伤的保护作用,取72只昆明小鼠随机分为对照组,四氯化碳(CCl4)模型组,阳性对照(联苯双酯)组,铁棍山药多糖低、中、高剂量组,每组12只,灌胃处理后使用CCl4制备急性肝损伤小鼠模型,观察各组形态学变化,同时测定生化指标。实验结果显示,经铁棍山药多糖处理的小鼠的肝损伤程度明显轻于模型组,铁棍山药多糖能降低小鼠血清中谷丙转氨酶(ALT)和谷草转氨酶(AST)含量,提高超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)的活性,降低丙二醛(MDA)、一氧化氮(NO)、肿瘤坏死因子-α(TNF-α)的含量。本研究结果表明,铁棍山药多糖对CCl4所诱导的小鼠肝损伤起到一定的保护作用。     

Adaptive characteristics of salt-induced myceloids of Arthrobacter globiformis

When Arthrobacter globiformis is grown in medium containing increased concentrations of NaCl or decreased levels of cations, the bacteria grow as clusters of branching myceloid cells. The sensitivities of salt-induced and citrate-induced myceloids to several environmental stresses were compared to those of normal exponential-phase bacilli and stationary-phase cocci. Salt-induced myceloids were more resistant than normal cells to ultraviolet light or heat shock at 45°C but not to osmotic upshock or pH 4.3; citrate-induced myceloids showed an intermediate rate of heat inactivation. Carbon or nitrogen starvation of myceloids in the absence of added NaCl or citrate led to their division into single cells. Both myceloids and the single cells derived from them were more resistant than normal bacteria to nitrogen starvation. Salt-induced and citrate-induced myceloids showed reduced metabolism of many different carbon compounds in Biolog GP plates. These studies suggest that the formation of multicellular structures by A. globiformis is an adaptive response which increases its potential for survival.     

脂氧素受体激动剂BML-111对大鼠急性肝损伤的干预作用及其机制*

目的: 探索脂氧素对急性肝损伤的作用及机制。方法: SD大鼠24只随机分为4组(n=6):正常对照组:皮下注射橄榄油,剂量1.8 ml/kg。模型组:皮下注射40%四氯化碳(CCL4)油剂(橄榄油为溶剂),剂量3 ml/kg。BML-111治疗组:皮下注射Lipoxin受体激动剂BML-111,剂量1 mg/kg,30 min后处理同模型组。BOC-2阻断剂组:皮下注射Lipoxin受体阻断剂BOC-2,剂量50 μg/kg,30 min后处理同BML-111组。HE染色观察肝组织病理学变化,判断肝损伤情况。血清学检测血清谷丙转氨酶(ALT)及谷草转氨酶(AST)活性;试剂盒法检测大鼠肝组织中髓过氧化物酶(MPO)活性;ELISA法测定血清中血管紧张素转化酶(ACE)、血管紧张素转化酶2(ACE2)、血管紧张素II(AngII)、血管紧张素1-7(Ang-(1-7))的含量。Western blot检测肝组织中Ang II、Ang-(1-7)的蛋白含量。结果: 治疗组较模型组和阻断剂组的肝损伤程度减轻;BML-111降低CCL4损伤的大鼠血清中ACE、AngII的含量(P＜0.01)及升高血清中ACE2、Ang-(1-7)的含量(P＜0.01)。BML-111增加肝组织中Ang-(1-7)含量,降低CCL4损伤的大鼠组织中AngII含量。结论: 结果表明脂氧素受体激动剂BML-111对大鼠急性肝损伤的干预作用及其机制,可能与调节AngII和Ang-(1-7)有关。     

The effects of dietary flaxseed on the Fischer 344 rat. III. Protection against CCl(4)-induced liver injury

The hepatotoxic effect of carbon tetrachloride (CCl(4)) administered by gavage at 0.25 ml CCl(4) (1:1 in olive oil) per 100 g body weight was examined 24 h later in regular chow fed (RC) and 10% flax chow fed (FC) male and female Fischer 344 rats. CCl(4)-treated RC rats were subdued, lethargic and unkempt. CCl(4)-treated FC rats were much less affected. CCl(4) treatment resulted in loss of weight in RC and FC rats. In males, the weight loss was 6.7% body mass in RC rats compared to 5.6% body mass in FC rats. In females, the weight loss was 7.5% body mass in both RC and FC rats. While CCl(4) treatment increased the level of the liver injury marker plasma alanine aminotransferase (ALT) in RC rats, this CCl(4) effect was significantly attenuated in FC rats. In male rats, the ALT increase was 435-fold in RC rats and 119-fold in FC rats, over that of their respective controls. In female rats, the ALT increase was 454-fold in RC rats and 381-fold in FC rats, over that of their respective controls. These results provide evidence that flax consumption protects the liver against injury and that the extent of the protection is sex dependent. CCl(4) had no effect on the plasma level of gamma-glutamyltranspeptidase (gammaGT) in RC and FC rats supporting the contention that plasma gammaGT is not a useful marker for acute liver injury which is seen in this model. The activity of gammaGT was increased in the livers of FC rats compared to RC rats: 2.7-fold in males and 1.5-fold in females. In RC rats, the activity of liver gammaGT was decreased by CCl(4) treatment: 70% in the male and 25% in the female. However, this CCl(4) effect was reversed or abolished by flax consumption. Compared to RC rats: in male FC rats, CCl(4) actually increased the activity of liver gammaGT 1.28-fold; while in female FC rats, the depressing effect of CCl(4) treatment was abolished. The flax-induced preservation of gammaGT in the liver in response to injury may be involved in the observed hepatoprotection through generation of GSH. In RC male rats, CCl(4) treatment effected a 25% reduction in plasma glucose levels. There was no decrease in CCl(4)-treated FC male rats. In female rats, CCl(4) treatment effected a 21% decrease in plasma glucose levels in both RC and FC rats. In conclusion, multiple parameters for acute CCl(4)-induced injury were attenuated in the FC compared to the RC rat. That flaxseed consumption conferred greater protection against liver injury in the male than in the female suggests an involvement of the estrogenic lignan component of flaxseed. We discuss the possibility that this hepatoprotection is through a flax lignan-induced increase in reduced glutathione related to a flax effect on the activity of liver gammaGT in the resting state and the maintenance of its activity in response to injury.     

Hepatic calcium-binding protein regucalcin is released into the serum of rats administered orally carbon tetrachloride

The change in calcium-binding protein regucalcin, mainly localized in liver, in the liver and serum of rats received a single oral administration of carbon tetrachloride (50%; 1.0 ml/100 g body weight) was investigated. The change of regucalcin mRNA levels in the liver was analyzed by Northern blotting using liver regucalcin cDNA (0.6 kb). At 10 and 24 h after the administration, liver regucalcin mRNA levels were reduced markedly. Moreover, regucalcin concentration in the liver and serum was estimated by enzyme-linked immunoadsorbent assay (ELISA) with rabbit-anti-regucalcin IgG. Administration of carbon tetrachloride (CCl₄) induced a significant decrease in liver regucalcin concentration and a corresponding elevation of serum regucalcin concentration at 24 h after the administration. An appreciable increase in serum regucalcin concentration was seen at 2 h after the administration. Meanwhile, serum transaminases (GOT and GPT) activities were significantly increased by CCl₄ administration, indicating that liver injury is induced. The present study demonstrates that hepatic regucalcin is released into the serum of rats administered orally CCl₄, suggesting that the estimation of serum regucalcin is a useful tool for diagnosis of liver injury.     

Characterization and protection on acute liver injury of a polysaccharide MP-I from Mytilus coruscus

In this study, we analyzed a water-soluble polysaccharide MP-I isolated from Mytilus coruscus. MP-I was obtained by hot-water extraction, anion-exchange and gel-permeation chromatography. Complete hydrolysis, periodate oxidation, methylation analysis, as well as Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy were conducted to elucidate its structure. MP-I was subjected to investigate the protective effect on carbon tetrachloride (CCl(4)) induced liver damage in male Kunming mice. Based on the data obtained, MP-I was found to be an alpha-(1-->4)-D-glucan, branched with a single alpha-D-glucose at the C-6 position every eight residue, on average, along the main chain. Based on the calibration with Dextran, the glucan had a molecular weight of about 1.35 x 10(6) Da. Pharmacological studies revealed that MP-I could decrease serum alanine aminotransferase (ALT), serum aspartate aminotransferase (AST), and hepatic malondialdehyde aldehydes (MDA) levels, increase the hepatic total superoxide dismutase (T-SOD) activity, and improve hepatic damage in the CCl(4) induced liver injury in mice in a dose-dependent manner. The results suggest that the possible mechanism is due to its antioxidant activity of MP-I.     

Comparison of the Preventive Activity of Isorhamnetin Glycosides from Atsumi-kabu (Red Turnip,Brassica, campestris L.) Leaves on Carbon Tetrachloride-Induced Liver Injury in Mice

Isorhamnetin 3-O-glucoside, which was contained together with isorhamnetin 3,7-di-O-glucoside in atsumi-kabu leaves, suppressed increases in the plasma ALT and AST activities of mice with liver injury induced by the injection of carbon tetrachloride, but no suppression by isorhamnetin 3,7-di-O-glucoside was apparent. This result indicates that the release of glucose at the 7-position in isorhamnetin 3,7-di-O-glucoside was very important to mitigating liver injury.     

Probing the Catalytic Mechanism of Copper Amine Oxidase from Arthrobacter globiformis with Halide Ions

The catalytic reaction of copper amine oxidase proceeds through a ping-pong mechanism comprising two half-reactions. In the initial half-reaction, the substrate amine reduces the Tyr-derived cofactor, topa quinone (TPQ), to an aminoresorcinol form (TPQ_amr) that is in equilibrium with a semiquinone radical (TPQ_sq) via an intramolecular electron transfer to the active-site copper. We have analyzed this reductive half-reaction in crystals of the copper amine oxidase from Arthrobacter globiformis. Anerobic soaking of the crystals with an amine substrate shifted the equilibrium toward TPQ_sq in an “on-copper” conformation, in which the 4-OH group ligated axially to the copper center, which was probably reduced to Cu(I). When the crystals were soaked with substrate in the presence of halide ions, which act as uncompetitive and noncompetitive inhibitors with respect to the amine substrate and dioxygen, respectively, the equilibrium in the crystals shifted toward the “off-copper” conformation of TPQ_amr. The halide ion was bound to the axial position of the copper center, thereby preventing TPQ_amr from adopting the on-copper conformation. Furthermore, transient kinetic analyses in the presence of viscogen (glycerol) revealed that only the rate constant in the step of TPQ_amr/TPQ_sq interconversion is markedly affected by the viscogen, which probably perturbs the conformational change. These findings unequivocally demonstrate that TPQ undergoes large conformational changes during the reductive half-reaction.     

Purification and characterization of cyclic maltosyl-(1-->6)-maltose hydrolase and alpha-glucosidase from an Arthrobacter globiformis strain

Cyclic maltosyl-maltose [CMM, cyclo-[-->6)-alpha-D-Glcp-(1-->4)-alpha-D-Glcp-(1-->6)-alpha-D-Glcp-(1-->4)-alpha-D-Glcp-(1-->]], a novel cyclic tetrasaccharide, has a unique structure. Its four glucose residues are joined by alternate alpha-1,4 and alpha-1,6 linkages. CMM is synthesized from starch by the action of 6-alpha-maltosyltransferase from Arthrobacter globiformis M6. Recently, we determined the mechanism of extracellular synthesis of CMM, but the degrading pathway of the saccharide remains unknown. Hence we tried to identify the enzymes involved in the degradation of CMM to glucose from the cell-free extract of the strain, and identified CMM hydrolase (CMMase) and alpha-glucosidase as the responsible enzymes. The molecular mass of CMMase was determined to be 48.6 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and 136 kDa by gel filtration column chromatography. The optimal pH and temperature for CMMase activity were 6.5 and 30 degrees C. The enzyme remained stable from pH 5.5 to 8.0 and up to 25 degrees C. CMMase hydrolyzed CMM to maltose via maltosyl-maltose as intermediates, but it did not hydrolyze CMM to glucose, suggesting that it is a novel hydrolase that hydrolyzes the alpha-1,6-linkage of CMM. The molecular mass of alpha-glucosidase was determined to be 60.1 kDa by SDS-PAGE and 69.5 kDa by gel filtration column chromatography. The optimal pH and temperature for alpha-glucosidase activity were 7.0 and 35 degrees C. The enzyme remained stable from pH 7.0 to 9.5 and up to 35 degrees C. alpha-Glucosidase degraded maltosyl-maltose to glucose via panose and maltose as intermediates, but it did not degrade CMM. Furthermore, when CMMase and alpha-glucosidase existed simultaneously in a reaction mixture containing CMM, glucose was detected as the final product. It was found that CMM was degraded to glucose by the synergistic action of CMMase and alpha-glucosidase.     

四氯化碳诱导小鼠肝脏纤维化的差异蛋白质组学

以四氯化碳(Carbon tetrachloride,CCl4)诱导小鼠肝组织纤维化为研究模型,发现并探讨纤维化肝组织与正常肝组织在蛋白质组水平上的差异。实验小鼠(C57 BL/6)随机分为两组,由橄榄油和四氯化碳诱导15周,并分别对这两组肝组织的全蛋白表达谱进行质谱检测,应用GO(Gene Ontology)功能分类分析和KEGG(Kyoto Enyoolpedia of Genes and Genomes)信号通路的富集分析方法对鉴定到的全蛋白表达谱进行差异表达分析。在对照组和实验组中,我们分别鉴定到17 382和20 486条特异性肽段,图谱平均利用率大于50%,共计鉴定到蛋白4 991种(蛋白特异性肽段个数至少为1),其中差异表达蛋白有2 135种(差异倍数大于或等于2),表达上调蛋白1 264种,下调蛋白871种。纤维化肝脏组织中与细胞外基质组成(Extracellular matrix organization)、细胞骨架组成(Cytoskeleton organization)、有机磷酸代谢(Organophosphate metabolic process)、细胞定位(Cellular localization)和细胞组分调节(Regulation of cellular component organization)相关蛋白的表达是上调的;另外,与小分子代谢(Small molecule metabolic process)、蛋白质转运(Protein transport)和有机氮化合物的代谢(Organonitrogen compound metabolic process),以及四吡咯的合成过程(Tetrapyrrole biosynthetic process)有关蛋白的表达是下调的。信号通路富集分析结果表明,纤维化与VEGF和T细胞受体信号调节通路密切相关。结果提示,纤维化的形成不仅是一个复杂的信号转导过程,更是一个炎症与免疫相互促成的结果;增强肝实质细胞的存活,降低相关信号的传递及接收都有可能对纤维化的发生和发展起到抑制效果。     

Purification and Some Properties of Carboxylesterase from Arthrobacter globiformis; Stereoselective Hydrolysis of Ethyl Chrysanthemate

An esterase with excellent stereoselectivity for (+)-trans-ethyl chrysanthemate was purified to homogeneity from Arthrobacter globiformis SC-6-98-28. The purified enzyme hydrolyzed a mixture of ethyl chrysanthemate isomers stereoselectively to produce (+)-trans-acid with 100% stereoisomeric purity. The apparent molecular weight of the purified enzyme was 43,000 on SDS–polyacrylamide gel electrophoresis, and 94,000 on gel filtration chromatography. The optimum conditions for the ester hydrolysis were pH 10.0 at 45°C. The purified esterase hydrolyzed short-chain fatty acid esters, but did not have detectable activity on long-chain water-insoluble fatty acid esters. The enzyme activity was inbibited by diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride.     

蟛蜞菊内酯对四氯化碳致小鼠肝损伤的保护作用

目的:研究中药活性物质蟛蜞菊内酯的保肝作用及其机制。方法:采用小鼠腹腔注射CCl4制作肝损伤模型,测定小鼠血清中谷丙转氨酶(ALT)、谷草转氨酶(AST)、丙二醛(MDA),谷胱甘肽(GSH)和超氧化物歧化酶(SOD)指标,进行肝脏的组织病理学检查,观察蟛蜞菊内酯对CCl4所致肝损伤的保护作用。结果:蟛蜞菊内酯能明显降低肝损伤小鼠的血清ALT、AST和肝组织匀浆中MDA含量,SOD活力增强,明显减轻肝组织变性。结论蟛蜞菊内酯对CCl4引起的肝损伤有明显的保护作用,其机制可能与其抗氧化作用有关。     

Structural analysis of the elongation factor G protein from the low-temperature-adapted bacterium Arthrobacter globiformis SI55

The first structural analysis of elongation factor G (EF-G) from a cold-adapted bacterium is presented. EF-G is an essential protein involved in the elongation process during protein synthesis and is therefore thought to play a crucial role in the low-temperature adaptation of cold-adapted microorganisms. To define its importance, the EF-G gene (fus) from the psychrotolerant bacterium Arthrobacter globiformis SI55 was cloned and sequenced. The deduced primary structure of the elongation factor is composed of 700 amino acids with a predicted molecular mass of 77.4 kDa. A three-dimensional model of the protein was constructed based on the known crystal structures of structurally homologous proteins. Structural features that might potentially be important for activity and flexibility at low temperature were deduced by comparisons with models of the EF-G proteins from the closely related mesophiles Micrococcus luteus and Mycobacterium tuberculosis. These features include a loss in the number of salt bridges in intradomain and interdomain positions, increased solvent interactions mediated by greater charge and polarity on domain surfaces, loop insertions, loss of proline residues in loop structures, and an increase of hydrophobicity in core regions. Specific changes have also been identified in the catalytic domain (G domain) and sites of potential ribosome interaction, which may directly affect guanosine triphosphate (GTP) hydrolysis and elongation rates at low temperature. Received: September 20, 1999 / Accepted: December 2, 1999     

冬虫夏草菌丝提取物对化学性肝损伤的辅助保护作用

为明确冬虫夏草菌丝提取物对急性肝损伤小鼠谷丙转氨酶（ALT）、谷草转氨酶（AST）、肝细胞变性及坏死程度的影响,采用四氯化碳（CCl4）诱导小鼠急性化学性肝损伤模型,将动物随机分成5组,分别是空白对照组、模型组、冬虫夏草菌丝提取物低剂量组（1.11g/kg BW）、中剂量组（3.33g/kg BW）、高剂量组（10.00g/kg BW）,检测血清ALT、AST值,并取肝脏作病理切片,观察肝脏的病理损伤情况。冬虫夏草菌丝提取物高剂量组能明显降低CCl4急性肝损伤小鼠血清ALT值,减轻肝细胞坏死程度,表明冬虫夏草菌丝提取物对化学性肝损伤有辅助保护功能。     

Metabolism of isoflavones in human subjects

Isoflavones form a group of plant compounds that occur mainly in legumes, soy being the most important source in human diet. The high levels of isoflavones in the diet have been associated with a lowered risk for hormone-dependent diseases, including breast and prostate cancers, osteoporosis and cardiovascular disease. The metabolism of isoflavones in humans has been studied to a certain extent, but detailed studies are lacking. This paper reviews the current knowledge on metabolism of isoflavones and presents some preliminary results of a comprehensive soy feeding study, in which the phase I metabolites of soy isoflavones, daidzein, genistein and glycitein, were identified by GC-MS. This revised version was published online in June 2006 with corrections to the Cover Date.     

蛹虫草MF27高抗氧化活性提取物筛选及保肝作用研究

本研究对一株优质蛹虫草菌株MF27不同提取物进行体外抗氧化活性比较,筛选得到高抗氧化活性提取物,并进一步探究该提取物对CCl₄诱导的小鼠肝损伤的修复作用。以DPPH自由基和羟自由基的清除率为抗氧化评价指标,从菌丝体发酵液、菌丝体水提物/醇提物、以及子实体水提物/醇提物中筛选菌株MF27的高抗氧化活性提取物;以CCl₄致小鼠急性肝损伤为模型,通过检测血清生化指标、肝功指标的变化,来评价该高活性提取物的体内抗氧化保肝效果。体外抗氧化实验结果表明,MF27的不同提取物均具有较好的体外抗氧化活性,但对清除DPPH和OH自由基能力最好的提取物是子实体水提物,其对DPPH自由基的半数有效浓度（EC₅₀）为0.096mg/mL,对羟自由基的半数有效浓度（EC₅₀）为0.196mg/mL,当在1mg/mL 时对DPPH自由基的清除率为94.94%,对羟自由基的清除率为70.17%;体内抗氧化保肝结果显示,给药组（子实体水提物）相比模型组而言,小鼠血清中ALT、AST以及肝脏中MDA水平极显著降低（P<0.01）、SOD水平极显著升高（P<0.01）,表明子实体水提物能有效改善氧化性肝损伤,同时与阳性对照（联苯双酯）对比,给药组在肝脏指数上表现出相当的作用（P>0.05）。本研究表明菌株MF27的最有效抗氧化活性提取物是子实体水提物,它对体内氧化性肝损伤有一定的修复能力,揭示MF27子实体水提物具有成为抗氧化性肝损伤功能产品的潜力。     

黄根醇提物对小鼠实验性肝损伤保护作用的研究

以黄根醇提物为实验药物,对其进行了最大耐受量试验(MTD)和小鼠实验性急性肝损伤的研究,结果表明黄根醇提物最大耐受量为2080g生药/kg,并能显著降低CCL4、D-GalN所致的小鼠血清中ALT、AST升高(P<0.01);亦能明显降低BCG和LPS致免疫性肝损伤小鼠血清中ALT、AST及肝组织中的MDA的水平(P<0.01),增加肝组织中SOD的活性和GSH的水平(P<0.01)。该实验属首次报道。     

消炎痛对四氯化碳损伤大鼠肝的保护作用

本工作发现,消炎痛一次预处理能诱导大鼠肝脏对毒性物质损伤产生保护作用。用四氯化碳造成大鼠急性肝损伤模型,若预先皮下注射消炎痛一次,则血清谷丙转氨酶、胆红素及死亡率都显著降低,肝组织学检查也见损伤程度明显减轻。这一保护效应具有剂量依从关系,10mg/kg消炎痛剂量产生最好的保护效应。此种保护效应在消炎痛注射后12h左右产生,持续约一周。