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201.
Seong-Woo Choi Sun-Seog Kweon Jin-Su Choi Jung-Ae Rhee Young-Hoon Lee Hae-Sung Nam Seul-Ki Jeong Kyeong-Soo Park So-Yeon Ryu Hye-Rim Song Min-Ho Shin 《Journal of physiological anthropology》2015,34(1)
Background
Vitamin D plays an essential role in bone health and growth, but the optimal serum 25-hydroxyvitamin D (25(OH)D) concentration is not known. This study was performed to investigate the optimal 25(OH)D concentration in regard to parathyroid hormone (PTH) concentration in the Korean general population aged 50 years or older.Findings
The study population consisted of 8,857 subjects (3,545 men and 5,312 women) who participated in the baseline survey of the Dong-gu study, conducted in Korea between 2007 and 2010. Serum 25(OH)D and PTH concentrations were measured by chemiluminescent microparticle immunoassay. The optimal 25(OH)D concentration was estimated by using nonlinear regression model. Our data show that PTH concentration reached a theoretical plateau at 38.2 pg/ml and corresponding 25(OH)D concentration was 21.1 ng/ml in men and PTH concentration at 42.9 pg/ml and 25(OH)D concentration at 13.8 ng/ml in women.Conclusions
These results indicate that, for Korean general population aged 50 years or older, the optimal 25(OH)D concentration is 21.1 ng/ml in men and 13.8 ng/ml in women. 相似文献202.
Isolation and characterization of an arsenate-reducing bacterium and its application for arsenic extraction from contaminated soil 总被引:1,自引:0,他引:1
Chang YC Nawata A Jung K Kikuchi S 《Journal of industrial microbiology & biotechnology》2012,39(1):37-44
A Gram-negative anaerobic bacterium, Citrobacter sp. NC-1, was isolated from soil contaminated with arsenic at levels as high as 5,000 mg As kg−1. Strain NC-1 completely reduced 20 mM arsenate within 24 h and exhibited arsenate-reducing activity at concentrations as
high as 60 mM. These results indicate that strain NC-1 is superior to other dissimilatory arsenate-reducing bacteria with
respect to arsenate reduction, particularly at high concentrations. Strain NC-1 was also able to effectively extract arsenic
from contaminated soils via the reduction of solid-phase arsenate to arsenite, which is much less adsorptive than arsenate.
To characterize the reductase systems in strain NC-1, arsenate and nitrate reduction activities were investigated using washed-cell
suspensions and crude cell extracts from cells grown on arsenate or nitrate. These reductase activities were induced individually
by the two electron acceptors. This may be advantageous during bioremediation processes in which both contaminants are present. 相似文献
203.
Young‐Jin Son Chang‐Kyu Kim Young Bong Kim Dae‐Hyuk Kweon Yong‐Cheol Park Jin‐Ho Seo 《Biotechnology progress》2009,25(4):1064-1070
Insulin is a polypeptide hormone which is produced by the β‐cell of pancreas and controls the blood glucose level in the human body. Enzymatic modification of human proinsulin using trypsin and carboxypeptidase B generally causes high accumulation of insulin derivatives, leading to more complicated purification processes. A simple method including citraconylation and decitraconylation in the enzymatic modification process was developed for the reduction of a major derivative, des‐threonine human insulin. Addition of 3.0 g citraconic anhydride per g protein into the reaction solution led to the citraconylation of lysine residues in human proinsulin and reduction of relative des‐threonine insulin content from 13.5 to 1.0%. After the enzymatic hydrolysis of the citraconylated proinsulin, 100% of lysine residues can be decitraconylated and restored by adjusting pH to 2–3 at 25 °C. Combination of hydrogen peroxide addition and citraconylation of proinsulin expressed in recombinant Escherichia coli remarkably improved the conversion yield of insulin from 52.7 to 77.7%. Consequently, citraconylation of lysine residues blocked the unexpected cleavage of human proinsulin by trypsin, minimized the formation of des‐threonine insulin and hence increased the production yield of active insulin. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 相似文献
204.
205.
Tryptophan boost caused by senescence occurred independently of cytoplasmic glutamine synthetase 总被引:1,自引:0,他引:1
Park S Lee K Kang K Kim YS Lee S Kweon SJ Back K 《Bioscience, biotechnology, and biochemistry》2010,74(11):2352-2354
We examined to determine whether senescence-induced tryptophan levels are positively associated with levels of glutamine synthetase (GS1), the initial enzyme in tryptophan biosynthesis. We generated transgenic rice plants in which GS1 was suppressed by RNA interference technology. The transgenic line showed a dramatic decrease in GS1 protein and glutamine content, but the levels of tryptophan and mRNA of the key tryptophan biosynthetic genes upon senescence were comparable to those of the wild type. 相似文献
206.
Xylose-fermenting Saccharomyces strains are needed for commercialization of ethanol production from lignocellulosic biomass. Engineered Saccharomyces cerevisiae strains expressing XYL1, XYL2 and XYL3 from Pichia stipitis, however, utilize xylose in an oxidative manner, which results in significantly lower ethanol yields from xylose as compared to glucose. As such, we hypothesized that reconfiguration of xylose metabolism from oxidative into fermentative manner might lead to efficient ethanol production from xylose. To this end, we generated a respiration-deficient (RD) mutant in order to enforce engineered S. cerevisiae to utilize xylose only through fermentative metabolic routes. Three different repeated-batch fermentations were performed to characterize characteristics of the respiration-deficient mutant. When fermenting glucose as a sole carbon source, the RD mutant exhibited near theoretical ethanol yields (0.46 g g(-1)) during repeated-batch fermentations by recycling the cells. As the repeated-batch fermentation progressed, the volumetric ethanol productivity increased (from 7.5 to 8.3 g L(-1)h(-1)) because of the increased biomass from previous cultures. On the contrary, the mutant showed decreasing volumetric ethanol productivities during the repeated-batch fermentations using xylose as sole carbon source (from 0.4 to 0.3 g L(-1)h(-1)). The mutant did not grow on xylose and lost fermenting ability gradually, indicating that the RD mutant cannot maintain a good fermenting ability on xylose as a sole carbon source. However, the RD mutant was capable of fermenting a mixture of glucose and xylose with stable yields (0.35 g g(-1)) and productivities (0.52 g L(-1)h(-1)) during the repeated-batch fermentation. In addition, ethanol yields from xylose during the mixed sugar fermentation (0.30 g g(-1)) were higher than ethanol yields from xylose as a sole carbon source (0.21 g g(-1)). These results suggest that a strategy for increasing ethanol yield through respiration-deficiency can be applied for the fermentation of lignocellulosic hydrolyzates containing glucose and xylose. 相似文献
207.
Goo TW Yun EY Kim SW Choi KH Kang SW Shin KS Yu K Kwon OY 《Zeitschrift für Naturforschung. C, Journal of biosciences》2008,63(5-6):435-439
Protein disulfide isomerase (PDI) is an endoplasmic reticulum (ER)-localized multifunctional enzyme that can function as a disulfide oxidase, a reductase, an isomerase, and a chaperone. The domain organization of PDI is abb'xa'c, with two catalytic (CxxC) motifs and a KDEL ER retention motif. The members of the PDI family exhibit differences in tissue distribution, specificity, and intracellular localization. We previously identified and characterized the PDI of Bombyx mori (bPDI) as a thioredoxin-like protein that shares primary sequence homology with other PDIs. Here we compare the reactivation of inactivated rRNase and sRNase by bPDI and three bPDI mutants, and show that bPDI has mammalian PDI-like activity. On its own, the N-terminal a domain does not retain this activity, but the a' domain does. This is the first report of chaperone activity only in the a' domain, but not in the a domain. 相似文献
208.
High-temperature requirement A (HtrA) protein has been known as a moonlighting protein that plays dual roles as a molecular chaperone and as a protease. The proteolytic activity of HtrA is switched on at elevated temperatures, whereas the chaperone function predominates at normal temperatures. The temperature-regulated functional switch of HtrA appears to be critical for the control of the stability of cellular proteins, as well as for the elimination of denatured proteins in order to maintain viability. Although certain conformational changes are expected to be concurrent with the functional activation of HtrA proteolysis, the molecular mechanisms inherent to this process have yet to be elucidated. Spin labeling electron paramagnetic resonance and fluorescence spectroscopy experiments on the HtrA from Thermotoga maritima (Tm HtrA) have shown that a helical lid (HL) that covers the active site is lifted up to expose the catalytic and substrate-binding sites to the solvent at elevated temperatures, whereas the overall structure is maintained over a wide temperature range. Results indicate that the proteolytic activity of Tm HtrA is turned on by the geometric change occurring around the HL, resulting in a substrate-accessible path. In conclusion, the functional switch of Tm HtrA is embedded in the sentinel of the HL in terms of substrate accessibility. 相似文献
209.
Yoon SY Ha YE Choi JE Ahn J Lee H Kweon HS Lee JY Kim DH 《Journal of virology》2008,82(23):11976-11978
Coxsackievirus is the most important cause of meningitis and encephalitis in infants; an infection is sometimes fatal or may lead to neurodevelopmental defects. Here, we show that coxsackievirus B4 (CVB4) induces an autophagy pathway for replication in rat primary neurons. Notably, calpain inhibitors reduce autophagosome formation. Conversely, the inhibition of the autophagy pathway with 3-methyladenine inhibits calpain activation. This work reveals, for the first time, that calpain is essential for the autophagy pathway and viral replication in CVB4-infected neurons. 相似文献
210.
Maximum activity for phosphorylating C(2)-OH of the ascorbic acid was observed at the time of 16 h incubation from the culture of Flavobacterium devorans ATCC 10829. The enzyme was purified 1.178-fold, via ammonium sulfate fractionation, Fast Q anion exchange, and phenyl agarose chromatography. Gel chromatography and SDS-polyacrylamide electrophoresis experiments showed that the enzyme is a tetramer with subunit MW of 29 kDa. Among available second substrates, pyrophosphate showed the highest activity. Optimum temperature and pH were 45 degrees C and 5.5, respectively. The enzyme was chemically modified only by diethylpyrocarbonate and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), indicating that histidine and carboxylate are in the active site. pH studies showed that two histidines are involved in the binding of the substrates and a carboxylate in catalysis. Therefore, the chemical mechanism of the enzyme is likely that two histidines bind to pyrophosphate and carboxylate, respectively, and a carboxylate acts as a general base. 相似文献