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61.
Biochemical and catalytic properties of an endoxylanase purified from the culture filtrate of Sporotrichum thermophile 总被引:4,自引:0,他引:4
Katapodis P Vrsanská M Kekos D Nerinckx W Biely P Claeyssens M Macris BJ Christakopoulos P 《Carbohydrate research》2003,338(18):1881-1890
An endo-beta-1,4-xylanase (1,4-beta-D-xylan xylanoxydrolase, EC 3.2.1.8) present in culture filtrates of Sporotrichum thermophile ATCC 34628 was purified to homogeneity by Q-Sepharose and Sephacryl S-200 column chromatographies. The enzyme has a molecular mass of 25,000 Da, an isoelectric point of 6.7, and is optimally active at pH 5 and at 70 degrees C. Thin-layer chromatography (TLC) analysis showed that endo-xylanase liberates mainly xylose (Xyl) and xylobiose (Xyl2) from beechwood 4-O-methyl-D-glucuronoxylan, O-acetyl-4-O-methylglucuronoxylan and rhodymenan (a beta-(1-->4)-beta(1-->3)-xylan). Also, the enzyme releases an acidic xylo-oligosaccharide from 4-O-methyl-D-glucuronoxylan, and an isomeric xylotetraose and an isomeric xylopentaose from rhodymenan. Analysis of reaction mixtures by high performance liquid chromatography (HPLC) revealed that the enzyme cleaves preferentially the internal glycosidic bonds of xylooligosaccharides, [1-3H]-xylooligosaccharides and xylan. The enzyme also hydrolyses the 4-methylumbelliferyl glycosides of beta-xylobiose and beta-xylotriose at the second glycosidic bond adjacent to the aglycon. The endoxylanase is not active on pNPX and pNPC. The enzyme mediates a decrease in the viscosity of xylan associated with a release of only small amounts of reducing sugar. The enzyme is irreversibly inhibited by series of omega-epoxyalkyl glycosides of D-xylopyranose. The results suggest that the endoxylanase from S. thermophile has catalytic properties similar to the enzymes belonging to family 11. 相似文献
62.
The conserved residue Thr42 of -subunit of the chloroplast ATP synthase of maize (Zea mays L.) was substituted with Cys, Arg, and Ile, respectively, through site-directed mutagenesis. The over-expressed and refolded -proteins were purified by chromatography on DEAE-cellulose and FPLC on mono-Q column, which were as biologically active (inhibiting Ca2+-ATPase activity and blocking proton gate) as the native subunit isolated from chloroplasts. The T42C and T42R showed higher inhibitory activities on the soluble CF1(–) Ca2+-ATPase than the WT. The T42I inhibited the Ca2+-ATPase activity of soluble CF1 and restored photophosphorylation activity of membrane-bound CF1 deficient in the most efficiently. Far-ultraviolet CD spectra showed that the portions of -helix and -sheet structures of the three mutants were somewhat different from WT. Thus the conserved residue Thr42 may be important for maintaining the structure and function of the -subunit and the basic functions of the -subunit as far as an inhibitor of Ca2+-ATPase and the proton gate are related. 相似文献
63.
Li Y Shimizu H Xiang SL Maru Y Takao N Yamamoto K 《Biochemical and biophysical research communications》2002,299(5):697-702
c-Abl plays important roles in cellular response to DNA damage. However, possible roles for Arg (Abl-related gene) in DNA damage response are unknown. Here, we show that ionizing radiation (IR)-induced Rad51 focus formation is reduced in Arg-deficient cells generated from a chicken B cell line by targeted disruption. This is consistent with the findings that Arg-deficient cells display hypersensitivity to IR, elevated frequencies of IR-induced chromosomal aberrations, and reduced targeted integration frequencies. All of these abnormalities in DNA damage repair are also observed in ATM-deficient cells but not in c-Abl-deficient cells. Finally, we show that Arg interacts with and phosphorylates Rad51 in 293T cells. These results suggest that Arg plays a role in homologous recombinational (HR) DNA repair by phosphorylating Rad51. 相似文献
64.
Measurement of CTL-induced cytotoxicity: The caspase 3 assay 总被引:2,自引:0,他引:2
Jerome KR Sloan DD Aubert M 《Apoptosis : an international journal on programmed cell death》2003,8(6):563-571
Cytotoxic T lymphocytes (CTL) are critical effector cells of the immune system. Measurement of target cell damage has historically been an important measure of CTL function. CTL kill their target cells predominantly by inducing programmed cell death, or apoptosis. The gold standard for CTL-mediated cytotoxicity has been the 51Cr release assay. However, measurement of target cell lysis by 51Cr release does not provide mechanistic information on the fate of target cells, especially at the single cell level. Given the recent advances in our understanding of programmed cell death, newer assays are required which evaluate the status of the apoptotic pathways in target cells. We have developed a flow cytometry-based assay for CTL-mediated cytotoxicity based on specific binding of antibody to activated caspase 3 in target cells. Our assay is convenient and more sensitive than the 51Cr release assay. The use of this assay should allow mechanistic studies of the intracellular events resulting from CTL attack. 相似文献
65.
Popykina N. A. Gladysheva I. P. Zamolodchikova T. S. Larionova N. I. 《Russian Journal of Bioorganic Chemistry》2003,29(6):550-555
The interaction of duodenase, a new serine protease from a small group of Janus-faced proteases, with serpins, 1-protease inhibitor (1-PI) and antichymotrypsin (ACT) from human blood serum, was studied. The stoichiometry of the inhibition process was found to be 1.2 and 1.3 mol/mol for 1-PI and ACT, respectively. The presence of a stable enzyme–inhibitory complex duodenase–1-PI was confirmed by SDS-PAGE. The formation of the duodenase–ACT complex was not demonstrated; instead, the band of the cleaved inhibitor indicated the ACT hydrolysis. The suicide mechanism of the duodenase interaction with the human blood serpins was proved. The association rate constants (k
× 105, –1 s–1) were 2.4 ± 0.3 × 105 for 1-PI and 3.0 ± 0.4 × 105 for ACT. These results indicate the possibility of the regulation of duodenase activity by endogenous serpins. 相似文献
66.
Hygiene related health hazards in the home include ingestion of microorganisms or toxins, inhalation of toxins, allergens or microorganisms and infections through the skin. Bacteria, fungi and viruses may all be involved. For any particular family these hazards translate into different risks ranging from mild irritations to serious health threats. These will require different responses in terms of hygiene practice and hygiene product use. The consumer needs help to identify which hazards in his/her home pose a high risk and which are insignificant. Risk analysis techniques especially HACCP (Hazard analysis—critical control point) have been proven as effective tools in controlling hazards in the food industry. We have applied HACCP principles to a risk analysis of a typical home. We conclude that further studies are warranted and to focus on particular groups (e.g. families with infants, pensioners). Such information could be valuable in drawing up hygiene codes of practice and for forming the basis of educational material aimed at different target groups. 相似文献
67.
Catherine Michaux Jenny Pouyez Aurélie Mayard Pierre Vandurm Isabelle Housen Johan Wouters 《Biochimie》2010
In this study, the crystal structure of a novel endo-1,4-β-xylanase from Scytalidium acidophilum, XYL1, was solved at 1.9 Å resolution. This is one of the few solved crystal structures of acidophilic proteins. The enzyme has the overall fold typical to family 11 xylanases. Comparison of this structure with other homologous acidophilic, neutrophilic and alkalophilic xylanases provides additional insights into the general features involved in low pH adaptation (stability and activity). Several sequence and structure modifications appeared to be responsible for the acidophilic characteristic: (a) the presence of an aspartic acid H bonded to the acid/base catalyst (b) the nature of specifically conserved residues in the active site (c) the negative potential at the surface (d) the decreased number of salt bridges and H bonds in comparison with highly alkaline enzymes. 相似文献
68.
《Revista espa?ola de geriatría y gerontología》2022,57(3):174-181
Background and objectivesThe ageing population and the increasing dependency associated with it, makes the caregiver a highly relevant figure nowadays. The present study analyzes the socio-demographic differences between family and professional caregivers and their satisfaction and implication in a training program for caregivers.MethodsThe sample consisted of 59 caregivers of older people (37 were family caregivers and 22 professional caregivers) which received and implemented a caregivers training program in their daily care functions. These caregivers were trained in communication skills and cognitive stimulation strategies so they could use them in their daily care activities with the older adults under their care during a period of 3 months. All the participants were assessed with a socio-demographic questionnaire, 2 questionnaires to analyze their satisfaction with their work and the training received and one questionnaire to analyze their ability to detect and react to memory and behavior problems in the older adults they attended.ResultsThe results showed socio-demographic differences, improvements in satisfaction in family caregivers and a greater commitment in their daily work after the treatment in both groups although these effects could be due to different reasons.ConclusionsThe research shows the benefits of carrying out training programs for caregivers as they significantly increase the quality and satisfaction with caregiving. The study also displays the need to adjust such programs taking into account that the socio-demographic characteristics and training needs are different depending on whether de caregiver is a family member or a professional. 相似文献
69.
Gene encoding aspartyl dipeptidase from Xenopus levies (PepExl) is upregulated by thyroid hormone and is proposed to play a significant role in resorption of tadpole tail during metamorphosis. However, the importance of peptidase activity for the resorption of the tail remain elusive. Here we report the crystal structures of first eukaryotic S51 peptidase, PepExl, in its ligand-free and Asp-bound states at 1.4 and 1.8 Å resolutions, respectively. The active site is located at dimeric interface and the catalytic triad is found to be dissembled in ligand-free and assembled in Asp-bound state. Structural comparison and molecular dynamic simulations of ligand-free and Asp-bound states shows that distinct loop (loop-A) plays an important role in active site shielding, substrate binding and enzyme activation. This study illuminates the Asp-X dipeptide binding in PepExl is associated with ordering of the loop-A and assembly of residues of catalytic triad in active conformation for enzymatic activity. 相似文献
70.