排序方式: 共有13条查询结果,搜索用时 31 毫秒
1.
Hyung Kwoun Kim Hwa Jung Choi Myung Hee Kim Cheon Bae Sohn Tae Kwang Oh 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2002,1583(2):205-212
A lipase-producing Bacillus pumilus strain (B26) was isolated from a soil sample collected in Korea. The cloned gene showed that the lipase B26 composed of a 34-amino-acid signal sequence and a 181-amino-acid mature part corresponding to a molecular mass (Mr) of 19,225. Based on the Mr and the protein sequence, the lipase B26 belongs to the lipase family I.4. The optimum temperature and pH of the purified enzyme were 35 °C and 8.5, respectively. The lipase B26 showed a ‘Ca2+-independent thermostability and catalytic activity’. These are novel properties observed for the first time in lipase B26 among all bacterial lipases and correspond with the suggestion that this enzyme had no Ca2+-binding motif around the catalytic His156 residue. This enzyme seems to be a true lipase based on the experimental results that it could hydrolyze various long-chain triglycerides (C14–C18) and triolein (C18:1) and that it showed a typical interfacial activation mechanism toward both tripropionin and p-nitrophenyl butyrate. 相似文献
2.
Clifford S. Morrison William B. Armiger David R. Dodds Jonathan S. Dordick Mattheos A.G. Koffas 《Biotechnology advances》2018,36(1):120-131
Industrial enzymatic reactions requiring 1,4-NAD(P)H2 to perform redox transformations often require convoluted coupled enzyme regeneration systems to regenerate 1,4-NAD(P)H2 from NAD(P) and recycle the cofactor for as many turnovers as possible. Renewed interest in recycling the cofactor via electrochemical means is motivated by the low cost of performing electrochemical reactions, easy monitoring of the reaction progress, and straightforward product recovery. However, electrochemical cofactor regeneration methods invariably produce adventitious reduced cofactor side products which result in unproductive loss of input NAD(P). We review various literature strategies for mitigating adventitious product formation by electrochemical cofactor regeneration systems, and offer insight as to how a successful electrochemical bioreactor system could be constructed to engineer efficient 1,4-NAD(P)H2-dependent enzyme reactions of interest to the industrial biocatalysis community. 相似文献
3.
The current status of the L5178Y/TK+/-→TK-/- mouse-lymphona mutagenicity assay is described. Dose-survival-mutagenic response data are shown for 43 chemicals. Mutagenicity and cytotoxicity in the presence or absence of non-induced and/or Aroclor-induced rat-liver S-9 are compared for most of these chemicals. 25 of these for which usable carcinogenicity data exist have been used to construct an approximately linear relationship between oncogenic potency in vivo and mutagenic potency in this system in vitro; linearity between these two endpoints extends over a greater than 100 000-fold range in potencies. Several carcinogens which are negative or difficult to detect in the standard Ames assay are mutagenic in this mammalian cell system. These include natulan, sodium saccharin (lot S-1022), p,p′-DDE (a metabolite of DDT), dimethylnitrosamine, diethylnitrosamine and diethylstilbestrol. 相似文献
4.
K. Winnefeld H. Dawczynski W. Schirrmeister G. Adam U. Friedrich S. Hein 《Biological trace element research》1995,50(2):149-155
Selenium values of serum and whole blood were determined for two groups of patients undergoing large surgical interventions
(e.g., gastrectomy) and receiving a total parenteral nutrition (TPN). All patients showed low selenium values at the beginning
of TPN. The first group received a supplementation of selenium, and it was established that selenium levels normalized after
6–7 d. The balances of selenium turned out to be positive in all cases. The second group, which was not administered selenium
supplementation, showed significantly lower values of selenium. It can, therefore, be concluded that a substitution of selenium
prior to large surgical interventions following TPN clearly helps patients combat the increase in the oxidant stress reactions. 相似文献
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6.
Szpetnar M Matras P Kiełczykowska M Horecka A Bartoszewska L Pasternak K Rudzki S 《Cell biochemistry and function》2012,30(3):211-216
Total parenteral nutrition (TPN) is essential for patients with postoperative impairing gastrointestinal function who are unable to receive and absorb oral/enteral feeding for at least 7 days. Oxidative stress plays a major role in the ethiopathogenesis of cancers. In this study, total antioxidant status (TAS), glutathione peroxidase (GPx), superoxide dismutase, malondialdehyde and ascorbic acid were studied in patients operated because of small intestine, colorectal or pancreatic cancer and subsequently receiving TPN in comparison with patients receiving standard nutrition after the operation. TAS level and GPx activity were decreased in patients with small intestine cancer but did not differ in patients with colorectal and pancreatic cancer before and after surgery. In all patient groups receiving TPN, superoxide dismutase activity after the surgery was kept at the same level as before. On the fifth day after the surgery, malondialdehyde concentration in each group was restored to the value observed before surgery. On the fifth day of TPN treatment, ascorbic acid concentration was increased in every group of patients. TPN applied during the postoperative period alleviates oxidative stress resulting from surgery. In the case of small intestine cancer, the addition of vitamins and antioxidants to the nutrition mixture seems to result in depletion of antioxidant enzymes' activities. 相似文献
7.
Nicholas R. Rhodes Sharifa Love Yuan Chen Jasmina Hira Julia Kent Jane F. Rasco 《Journal of inorganic biochemistry》2010,104(7):790-797
The results of the current study indicate that diabetic rats have increased urinary Cr loss as a result of their diabetes; however, this increased urinary Cr loss is offset by increased absorption of Cr. Insulin resistant, obese rats have alterations in the rates of Cr transport and distribution compared to lean rats but have similar levels of urinary Cr loss and Cr absorption. Thus, any increases in urinary Cr loss associated with insulin resistance or diabetes are offset by increased absorption. Given that dietary chromium is normally absorbed with only ∼ 1% efficiency, suitable Cr exists in the diet so that a standard diet possesses sufficient chromium to allow for the increases in absorption associated with diabetes. Consequently, supplementing the diet with nutritionally relevant quantities of chromium is not anticipated to have any beneficial effects. Similarly, beneficial effects on plasma variables, such as cholesterol, triglycerides, and insulin concentrations, from supra-nutritional doses of Cr(III) complexes should not arise from alleviation of chromium deficiency. These beneficial effects must arise from pharmacological effects of high dose Cr(III) administration. 相似文献
8.
Qualitative and quantitative assay were developed to study the in vitro enzymatic activation of dimethylnitrosamine (DMNA) to its mutagenic form. Three different fractions from mouse liver homogenates, including purified microsomes, were employed for the activation, and several parameters of the assay were investigated. Qualitative tests were conducted to measure the ability of hepatic enzymes obtained from six mammalian specie to activate DMNA. A comparison between two inbred mouse strains using the in vitro activation assay demonstrated that this technique might be a useful tool in quantitatively measuring differences in genetically influenced levels of DMNA metabolism in individual animals and their tissues. 相似文献
9.
In order to mimic the surface of parenteral nutrition emulsion droplets, the first molecular dynamics simulation of a palmitoyloleoylphosphatidylcholine (POPC) monolayer at a water/triglyceride (trilinoleoylglycerol, LLL) interface was performed. Triglyceride influence was evaluated by comparing computed phospholipid properties to the ones in a similarly modelled hydrated POPC bilayer. As expected, polar head properties (molecular area, lipid hydration, headgroup orientation) were not affected by triglycerides. In contrast, slight differences were observed on phospholipid alkyl tail region (order parameter, diffusion, Van der Waals interactions). This first approach can reasonably be extended to a further more realistic multicomponent model of clinical nutrition emulsions. 相似文献
10.
目的:评价早期肠内营养(EEN)对胃癌根治术患者术后恢复和免疫功能的影响。方法:选入2011年6月~2014年1月在我院行胃癌根治术治疗的患者60例,根据术后营养方式不同分为EEN组和全肠外营养支持(TPN)组,每组30例。比较两组患者机体恢复及免疫功能情况。术后随访3年,观察并记录两组无进展生存率和总生存率。结果:EEN组术后排气时间[(2.46±0.78)d vs(3.85±1.03)d]、排便时间[(4.03±1.17)d vs(5.67±1.23)d]、进流质时间[(5.88±1.30)d vs(7.26±1.59)d]、进半流食时间[(7.94±1.85)d vs(11.01±2.36)d]和住院天数[(14.87±2.56)d vs(17.54±3.30)d]均显著短于TPN组,差异均有统计学意义(P0.05)。术后第1d,两组各项体液免疫指标(Ig A、Ig G、Ig M浓度)和细胞免疫指标(CD3+、CD4+和CD4+/CD8+水平)均显著下降(P0.05),营养支持后逐渐恢复,而EEN组恢复幅度较TPN组大,差异具有统计学意义(P0.05)。EEN组术后并发症总发生率显著低于TPN组(13.33%vs 36.67%,P0.05)。EEN组患者1年、2年和3年无进展生存率和总生存率均稍高于TPN组,但差异无统计学意义(P0.05)。结论:EEN可有效促进胃癌根治术患者的肠功能恢复,缩短住院时间,提高机体免疫功能,降低并发症的发生,值得在临床推荐应用。 相似文献