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91.
Biotechnological approaches for L-ascorbic acid production 总被引:3,自引:0,他引:3
Over the past decade there has been increasing pressure to develop alternatives to the Reichstein process, a largely chemical synthesis by which the vast majority of world vitamin C (L-ascorbic acid, L-AA) is produced. The pressures include increasing environmental concerns and legislation, and the need to increase process efficiency and reduce capital costs. The development of efficient fermentation processes in the past ten years has also represented a catalyst for change. Here, we describe the development of biotechnological alternatives for the synthesis of Reichstein intermediates by industrial microorganisms. The recent elucidation of the plant biosynthetic pathway represents new opportunities not only for the direct synthesis of L-AA by fermentation but also for the production of human crop plants and animal fodder with enhanced nutritional value. We discuss the potential for these developments in the light of recent findings concerning L-AA biosynthesis in plants. 相似文献
92.
The kinesin-related protein MCAK is a microtubule depolymerase that forms an ATP-hydrolyzing complex at microtubule ends 总被引:12,自引:0,他引:12
MCAK belongs to the Kin I subfamily of kinesin-related proteins, a unique group of motor proteins that are not motile but instead destabilize microtubules. We show that MCAK is an ATPase that catalytically depolymerizes microtubules by accelerating, 100-fold, the rate of dissociation of tubulin from microtubule ends. MCAK has one high-affinity binding site per protofilament end, which, when occupied, has both the depolymerase and ATPase activities. MCAK targets protofilament ends very rapidly (on-rate 54 micro M(-1).s(-1)), perhaps by diffusion along the microtubule lattice, and, once there, removes approximately 20 tubulin dimers at a rate of 1 s(-1). We propose that up to 14 MCAK dimers assemble at the end of a microtubule to form an ATP-hydrolyzing complex that processively depolymerizes the microtubule. 相似文献
93.
Faghih R Dwight W Pan JB Fox GB Krueger KM Esbenshade TA McVey JM Marsh K Bennani YL Hancock AA 《Bioorganic & medicinal chemistry letters》2003,13(7):1325-1328
Novel 4'-[(NR1R2-1-yl)]-propoxy-biaryl-4-carboxamides were designed and synthesized. All compounds were tested for affinity at histamine H(3)receptors. Most compounds were highly potent and selective for human and rat H(3) receptors and selected examples such as A-349821 showed functional antagonism of H(3) receptors in vitro and in a mouse dipsogenia model. 相似文献
94.
Arora RC Hirsch GM Johnson Hirsch K Hancock Friesen C Armour JA 《American journal of physiology. Regulatory, integrative and comparative physiology》2001,280(6):R1736-R1740
We sought to determine the behavior of intrinsic cardiac neurons in human subjects undergoing cardiac surgery and to correlate their activity with hemodynamics status. A lead II electrocardiogram, pulmonary artery pressure, and systemic arterial pressure were recorded along with extracellular activity generated by right atrial neurons in 10 patients undergoing coronary artery bypass surgery. Identified neurons generated spontaneously activity that was, for the most part, unrelated to the cardiac cycle. Most neurons were activated by gentle mechanical distortion of ventricular epicardial loci. The activity generated by neurons in each patient increased when arterial pressure increased and decreased when arterial pressure fell. Intrinsic cardiac neurons continued to generate activity during cardioplegia and cardiopulmonary bypass, but at reduced levels. Normal neuronal activity was restored postbypass. It is concluded that human intrinsic cardiac neurons generate spontaneous activity and that many receive inputs from ventricular mechanosensory neurites. The latter may account for the fact that their behavior depends, in part, on cardiac dynamics. They are also sensitive to intravenously administered pharmacological agents. These data also indicate that cardiopulmonary bypass and cardioplegia do not induce residual depression of their function. 相似文献
95.
Functional expression in Escherichia coli and membrane topology of porin HopE, a member of a large family of conserved proteins in Helicobacter pylori 下载免费PDF全文
HopE is one of the smallest members of a family of 31 outer membrane proteins in Helicobacter pylori and has been shown to function as a porin. In this study it was cloned into Escherichia coli where it was expressed in the outer membrane, as confirmed by indirect immunofluorescence using HopE-specific antibodies. HopE purified from E. coli reconstituted channels in planar bilayer membranes that were the same size as those formed by HopE purified from H. pylori. A model of the membrane topology of HopE was constructed and indicated that this protein formed a beta-barrel with 16 transmembrane amphipathic beta-strands. The accuracy of this model was tested by linker insertion mutagenesis, assuming that, like other porins, amino acid insertions were not tolerated in the transmembrane beta-strands but were tolerated in the adjoining loop regions. Generally, the results obtained with a series of 12 insertions of the sequence RSKDV and two substitutions were consistent with the topological model. The preponderance of amino acids that were conserved in the extended family of HopE paralogs were predicted to be within the membrane and comprised 45% of all residues in the membrane. 相似文献
96.
Scott MG Rosenberger CM Gold MR Finlay BB Hancock RE 《Journal of immunology (Baltimore, Md. : 1950)》2000,165(6):3358-3365
97.
NO way back: nitric oxide and programmed cell death in Arabidopsis thaliana suspension cultures 总被引:27,自引:2,他引:25
Clarke A Desikan R Hurst RD Hancock JT Neill SJ 《The Plant journal : for cell and molecular biology》2000,24(5):667-677
Recent research has implicated nitric oxide (NO) in the induction of the hypersensitive response (HR) during plant-pathogen interactions. Here we demonstrate that Arabidopsis suspension cultures generate elevated levels of NO in response to challenge by avirulent bacteria, and, using NO donors, show that these elevated levels of NO are sufficient to induce cell death in Arabidopsis cells independently of reactive oxygen species (ROS). We also provide evidence that NO-induced cell death is a form of programmed cell death (PCD), requiring gene expression, and has a number of characteristics of PCD of mammalian cells: NO induced chromatin condensation and caspase-like activity in Arabidopsis cells, while the caspase-1 inhibitor, Ac-YVAD-CMK, blocked NO-induced cell death. A well-established second messenger mediating NO responses in mammalian cells is cGMP, produced by the enzyme guanylate cyclase. A specific inhibitor of guanylate cyclase blocked NO-induced cell death in Arabidopsis cells, and this inhibition was reversed by the cell-permeable cGMP analogue, 8Br-cGMP, although 8Br-cGMP alone did not induce cell death or potentiate NO-induced cell death. This suggests that cGMP synthesis is required but not sufficient for NO-induced cell death in Arabidopsis. In-gel protein kinase assays showed that NO activates a potential mitogen-activated protein kinase (MAPK), although a specific inhibitor of mammalian MAPK activation, PD98059, which blocked H2O2-induced cell death, did not inhibit the effects of NO. 相似文献
98.
99.
100.
Apurva Bhargava Milan Osusky Benjamin S. Forward Robert E. Hancock William W. Kay Santosh Misra 《Plant Cell, Tissue and Organ Culture》2007,88(3):301-312
Antimicrobial cationic peptides provide a promising means of engineering plant resistance to a range of plant pathogens, including
viruses. PV5 is a synthetic structural variant of polyphemusin, a cationic peptide derived from the horseshoe crab-Limulus polyphemus. PV5 has been shown to be benign toward eukaryotic membranes but with enhanced antimicrobial activity against animal pathogens.
In this work, the cytotoxicity of PV5 toward tobacco protoplasts and leaf discs was assessed using TTC (2,3,5-triphenyltetrazolium
chloride) and Evans blue colorimetric assays. PV5 showed no measurable cytotoxic effects even at levels as high as 60 μg.
As a possible approach to enhancing plant resistance, a gene encoding PV5 was fused to the signal sequence encoding the C-terminus
portion of the BiP protein from Pseudotsuga menziesii, under the control of 2 × 35S CaMV promoter. When introduced into Nicotiana tabacum var Xanthi gene integration and expression was confirmed by both Southern and northern analyses. When transgenic plants were
subsequently challenged with bacterial and fungal phytopathogens enhanced resistance was observed. Moreover, transgenic plants
also displayed antiviral properties against Tobacco Mosaic Virus making PV5 an excellent candidate for conferring unusually
broad spectrum resistance to plants and the first anti-plant virus antimicrobial peptide. 相似文献