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1.
农田栽参根区土壤酶活性与土壤养分的关系 总被引：1，自引：0，他引：1
为深入了解农田栽参土壤肥力状况,运用典型相关分析法对农田栽参土壤中主要养分含量与4种土壤酶活性的关系进行了分析。结果表明:农田栽参根区土壤中磷酸酶、蔗糖酶和过氧化氢酶活性与有机质、全氮、全磷、速效磷以及有效钾含量显著相关,其中磷酸酶影响土壤中磷的形态,蔗糖酶对土壤有机质转化和氮、磷、钾的含量及形态具有重要作用,过氧化氢酶能够加速土壤有机质分解转化。土壤中锌对上述酶活性有一定的促进作用;土壤脲酶活性影响土壤中碱解氮含量,土壤中铁和铜影响土壤中尿酶活性。结合其他养分因子,综合土壤酶活性指标可以作为评价农田栽参土壤肥力的一个生物活性指标。 相似文献
2.
Coles CH Shen Y Tenney AP Siebold C Sutton GC Lu W Gallagher JT Jones EY Flanagan JG Aricescu AR 《Science (New York, N.Y.)》2011,332(6028):484-488
Heparan and chondroitin sulfate proteoglycans (HSPGs and CSPGs, respectively) regulate numerous cell surface signaling events, with typically opposite effects on cell function. CSPGs inhibit nerve regeneration through receptor protein tyrosine phosphatase sigma (RPTPσ). Here we report that RPTPσ acts bimodally in sensory neuron extension, mediating CSPG inhibition and HSPG growth promotion. Crystallographic analyses of a shared HSPG-CSPG binding site reveal a conformational plasticity that can accommodate diverse glycosaminoglycans with comparable affinities. Heparan sulfate and analogs induced RPTPσ ectodomain oligomerization in solution, which was inhibited by chondroitin sulfate. RPTPσ and HSPGs colocalize in puncta on sensory neurons in culture, whereas CSPGs occupy the extracellular matrix. These results lead to a model where proteoglycans can exert opposing effects on neuronal extension by competing to control the oligomerization of a common receptor. 相似文献
3.
One of six monoclonal antibodies raised against purified human placental alkaline phosphatase cross-reacts with the adult and fetal forms of intestinal alkaline phosphatase. The placental and intestinal enzymes are nonallelic. A new electrophoretic titration procedure was used to assess the relative reactivities of the different enzymes with the antibody. The placental enzyme was the most reactive. However, the adult intestinal enzyme showed greater reactivity than the fetal enzyme. The determinants to which the antibody binds on these three forms of alkaline phosphatase presumably differ in their detailed molecular configurations. 相似文献
4.
Chang CI Chelliah Y Borek D Mengin-Lecreulx D Deisenhofer J 《Science (New York, N.Y.)》2006,311(5768):1761-1764
Tracheal cytotoxin (TCT), a naturally occurring fragment of Gram-negative peptidoglycan, is a potent elicitor of innate immune responses in Drosophila. It induces the heterodimerization of its recognition receptors, the peptidoglycan recognition proteins (PGRPs) LCa and LCx, which activates the immune deficiency pathway. The crystal structure at 2.1 angstrom resolution of TCT in complex with the ectodomains of PGRP-LCa and PGRP-LCx shows that TCT is bound to and presented by the LCx ectodomain for recognition by the LCa ectodomain; the latter lacks a canonical peptidoglycan-docking groove conserved in other PGRPs. The interface, revealed in atomic detail, between TCT and the receptor complex highlights the importance of the anhydro-containing disaccharide in bridging the two ectodomains together and the critical role of diaminopimelic acid as the specificity determinant for PGRP interaction. 相似文献
5.
Interleukin-2 (IL-2) is an immunoregulatory cytokine that acts through a quaternary receptor signaling complex containing alpha (IL-2Ralpha), beta (IL-2Rbeta), and common gamma chain (gc) receptors. In the structure of the quaternary ectodomain complex as visualized at a resolution of 2.3 angstroms, the binding of IL-2Ralpha to IL-2 stabilizes a secondary binding site for presentation to IL-2Rbeta. gammac is then recruited to the composite surface formed by the IL-2/IL-2Rbeta complex. Consistent with its role as a shared receptor for IL-4, IL-7, IL-9, IL-15, and IL-21, gammac forms degenerate contacts with IL-2. The structure of gammac provides a rationale for loss-of-function mutations found in patients with X-linked severe combined immunodeficiency diseases (X-SCID). This complex structure provides a framework for other gammac-dependent cytokine-receptor interactions and for the engineering of improved IL-2 therapeutics. 相似文献
6.
锰对商陆根际微生物及土壤酶的影响 总被引：1，自引：0，他引：1
进一步阐明植物对锰毒的耐性机制,通过盆栽试验对不同Mn浓度下美洲商陆根际微生物及土壤酶活性的影响及用顺序浸提法研究商陆根际Mn形态与6种土壤酶的关系.结果表明:1)随Mn浓度的增加,真菌数量逐渐减少,细菌、放线菌数量变化呈波动性.2)低浓度Mn可刺激脲酶、磷酸酶的活性;高浓度下,脲酶、蛋白酶、转化酶、过氧化氢酶、磷酸酶活性均受到不同程度的抑制;多酚氧化酶活性在高浓度下增加.3)相关分析表明,锰浓度与土壤酶活性间存在显著负相关性,相关程度为过氧化氢酶＞脲酶＞磷酸酶＞多酚氧化酶＞蛋白酶＞转化酶;脲酶、蛋白酶、转化酶、多酚氧化酶、磷酸酶5种酶的活性间呈显著正相关,表明它们对锰胁迫有相似的适应性.过氧化氢酶、脲酶对锰的影响作用最敏感.4)土壤酶与锰化学形态多呈线性关系,各形态Mn与脲酶、磷酸酶、过氧化氢酶活性均呈显著或极显著负相关,而与转化酶活性的负相关性很小,全Mn与蛋白酶活性及专性吸附态Mn与多酚氧化酶活性的相关性显著.5)各形态锰含量与土壤酶活性的相关关系优于总量锰,因此可将锰各形态含量关系作为评价红壤锰污染程度的主要生物学指标. 相似文献
7.
不同水分条件下生物炭对红壤磷素形态及磷酸酶活性的影响 总被引：5，自引：2，他引：3
为探究土壤不同水分条件下生物炭对红壤磷素形态转化及磷酸酶活性的影响,以期为土壤磷素管理和生物炭合理利用提供参考。通过设置土壤不同含水量(33%、66%、100%)与生物炭添加量(0、0.5%、2%)进行培养试验,测定土壤的有效磷、各磷素形态(Al-P、Ca-P、Fe-P、O-P)及土壤酸性磷酸酶与碱性磷酸酶活性。结果表明:生物炭的施入显著提高了土壤有效磷含量;在培养前期,生物炭主要增加土壤中难溶态的Al-P含量,这主要是由生物炭带来的可溶性磷进入土壤中转化所导致;在培养后期,水分与生物炭都能够在一定程度上活化土壤中的Ca-P、Fe-P与O-P,释放更多磷素。生物炭本身呈碱性,添加到土壤中,有效中和了土壤酸度,使得土壤pH值上升2.82～3.13个单位,土壤酸性磷酸酶活性下降。此外,淹水条件能够降低土壤的酸性磷酸酶与碱性磷酸酶活性。研究表明,生物炭的添加能够有效提高土壤pH值、有效磷含量,同时降低土壤酸性磷酸酶的活性。 相似文献
8.
Liu T Liu Z Song C Hu Y Han Z She J Fan F Wang J Jin C Chang J Zhou JM Chai J 《Science (New York, N.Y.)》2012,336(6085):1160-1164
Pattern recognition receptors confer plant resistance to pathogen infection by recognizing the conserved pathogen-associated molecular patterns. The cell surface receptor chitin elicitor receptor kinase 1 of Arabidopsis (AtCERK1) directly binds chitin through its lysine motif (LysM)-containing ectodomain (AtCERK1-ECD) to activate immune responses. The crystal structure that we solved of an AtCERK1-ECD complexed with a chitin pentamer reveals that their interaction is primarily mediated by a LysM and three chitin residues. By acting as a bivalent ligand, a chitin octamer induces AtCERK1-ECD dimerization that is inhibited by shorter chitin oligomers. A mutation attenuating chitin-induced AtCERK1-ECD dimerization or formation of nonproductive AtCERK1 dimer by overexpression of AtCERK1-ECD compromises AtCERK1-mediated signaling in plant cells. Together, our data support the notion that chitin-induced AtCERK1 dimerization is critical for its activation. 相似文献
9.
养殖池塘底泥磷酸酶活性与释磷关系及其调控的研究 总被引：2，自引：0，他引：2
以天津市东丽区和西青区2个养殖池塘为对象,采用用室内试验方法,研究了底泥中各有机磷组分与上覆水中可溶性磷(DRP)含量、底泥磷酸酶活性与有机磷各组分及上覆水中可溶性磷之间的关系,并采取不同处理对底泥酸性磷酸酶(ACP)和碱性磷酸酶(ALP)活性进行调控.结果表明,底泥中活性有机磷(LOP)、中等活性有机磷(MLOP)、中稳性有机磷(MROP)与上覆水中DRP之间呈显著正相关.底泥中ALP与MLOP、MROP之间相关显著,并对其直接影响较大;ACP与MLOP之间相关显著,对其产生的直接影响也很大.A、B两池塘底泥中ALP与上覆水中DRP随时间变化规律基本一致,二者之间呈显著正相关.在养殖水体中加入酶抑制剂和沸石能抑制ALP和ACP活性,并以酶抑制剂加沸石的处理效果最好. 相似文献
10.
Human immunodeficiency virus type-1 (HIV-1) membrane fusion is promoted by the formation of a trimer-of-hairpins structure that brings the amino- and carboxyl-terminal regions of the gp41 envelope glycoprotein ectodomain into close proximity. Peptides derived from the carboxyl-terminal region (called C-peptides) potently inhibit HIV-1 entry by binding to the gp41 amino-terminal region. To test the converse of this inhibitory strategy, we designed a small protein, denoted 5-Helix, that binds the C-peptide region of gp41. The 5-Helix protein displays potent (nanomolar) inhibitory activity against diverse HIV-1 variants and may serve as the basis for a new class of antiviral agents. The inhibitory activity of 5-Helix also suggests a strategy for generating an HIV-1 neutralizing antibody response that targets the carboxyl-terminal region of the gp41 ectodomain. 相似文献
11.
G R Law 《Science (New York, N.Y.)》1967,156(3778):1106-1107
Two electrophoretic vari ants of leucine aminopeptidase show direct association with two genetically controlled forms of alkaline phosphatase. Treatment of plasma with neuraminidase converted the faster-migrating form of both enzymes to slower-moving forms, but plasmas with slowermigrating forms were unaffected by this treatment. The two forms of the enzymes may be due to the presence or absence of a single gene controlling the attachment of sialic acid to the enzyme molecules. 相似文献
12.
CLV1, which encodes a leucine-rich repeat receptor kinase, and CLV3, which encodes a secreted peptide, function in the same genetic pathway to maintain stem cell populations in Arabidopsis shoot apical meristem. Here, we show biochemical evidence, by ligand binding assay and photoaffinity labeling, that the CLV3 peptide directly binds the CLV1 ectodomain with a dissociation constant of 17.5 nM. The CLV1 ectodomain also interacts with the structurally related CLE peptides, with distinct affinities depending on the specific amino acid sequence. Our results provide direct evidence that CLV3 and CLV1 function as a ligand-receptor pair involved in stem cell maintenance. 相似文献
13.
B M Phelps P Primakoff D E Koppel M G Low D G Myles 《Science (New York, N.Y.)》1988,240(4860):1780-1782
The rate of lateral diffusion of integral membrane proteins is constrained in cells, but the constraining factors for most membrane proteins have not been defined. PH-20, a sperm surface protein involved in sperm-egg adhesion, was shown to be anchored in the plasma membrane by attachment to the lipid phosphatidylinositol and to have a diffusion rate that is highly restricted on testicular sperm, being more than a thousand times slower than lipid diffusion. These results support the hypothesis that lateral mobility of a membrane protein can be regulated exclusively by interactions of its ectodomain. 相似文献
14.
京北山地西段天然次生林林地土壤养分、磷酸酶活性及其相互关系研究 总被引：1，自引：0，他引：1
采用相关分析法,揭示京北西段天然次生林土壤磷酸酶活性与土壤养分的关系,以期为林地土壤肥力管理提供理论依据。结果表明:试验区土壤有机质处于极高水平,全氮处于高水平,有效氮、速效磷属于低水平。0-25 cm土层的土壤养分和磷酸酶活性比低层养分增加幅度约54.4%,且垂直递减规律明显;不同林型土壤磷酸酶均以酸性磷酸酶为主;经相关分析,土壤磷酸酶活性与土壤有机质、全氮、有效氮、有效磷和速效钾呈显著正相关。 相似文献
15.
Chemoattractant-regulated mobilization of a novel intracellular compartment in human neutrophils 总被引：22，自引：0，他引：22
A novel mobilizable intracellular compartment was identified in human neutrophils by latent alkaline phosphatase activity. This compartment is mobilized to the plasma membrane much more readily than any identified granule subset and has kinetics of up-regulation in the membrane similar to those reported for a variety of receptor proteins. Triton X-100 permeabilization of both intact human neutrophils and subcellular fractions obtained by density-gradient centrifugation revealed that 70 percent of the alkaline phosphatase is located in an intracellular compartment distinct from primary, secondary, and gelatinase granules and from the plasma membrane. This compartment fully translocates to the plasma membrane after stimulation with nanomolar concentrations of the chemotactic peptide N-formylmethionylleucylphenylalanine. 相似文献
16.
Phosphatase mutants in Aspergillus nidulans 总被引：1，自引：0，他引：1
G Dorn 《Science (New York, N.Y.)》1965,150(700):1183-1184
Three mutants at three different phosphatase loci produce inactive enzymes at 35 degrees C but partially or fully active enzynmes at 25 degrees C. Furthermore, a suppressor mutant (su5palA1) which restores alkaline phosphatase activity in the palA1 mtutant is an allele of palcC4, a mzutant with a simultaneous reduction in alkaline and acid phosphatase activity. These data suggest that the phosphataseproteins may be made up of two or more different polypeptide chains, and that some of the polypeptide chains are common to two or more of these enzymes. 相似文献
17.
Oxysterol-binding protein (OSBP) is the founding member of a family of sterol-binding proteins implicated in vesicle transport, lipid metabolism, and signal transduction. Here, OSBP was found to function as a cholesterol-binding scaffolding protein coordinating the activity of two phosphatases to control the extracellular signal-regulated kinase (ERK) signaling pathway. Cytosolic OSBP formed a approximately 440-kilodalton oligomer with a member of the PTPPBS family of tyrosine phosphatases, the serine/threonine phosphatase PP2A, and cholesterol. This oligomer had dual specific phosphatase activity for phosphorylated ERK (pERK). When cell cholesterol was lowered, the oligomer disassembled and the level of pERK rose. The oligomer also disassembled when exposed to oxysterols. Increasing the amount of OSBP oligomer rendered cells resistant to the effects of cholesterol depletion and decreased the basal level of pERK. Thus, cholesterol functions through its interaction with OSBP outside of membranes to regulate the assembly of an oligomeric phosphatase that controls a key signaling pathway in the cell. 相似文献
18.
Protein tyrosine phosphatase activity of an essential virulence determinant in Yersinia 总被引：81，自引：0，他引：81
Yersinia is the genus of bacteria that is the causative agent in plague or the black death, and on several occasions this organism has killed a significant portion of the world's population. An essential virulence determinant of Yersinia was shown to be a protein tyrosine phosphatase. The recombinant 50-kilodalton Yersinia phosphatase had a specificity for removal of phosphate from Tyr-containing as opposed to Ser/Thr-containing phosphopeptides and proteins. Site-directed mutagenesis was used to show that the Yersinia phosphatase possesses an essential Cys residue required for catalysis. Amino acids surrounding an essential Cys residue are highly conserved, as are other amino acids in the Yersinia and mammalian protein tyrosine phosphatases, suggesting that they use a common catalytic mechanism. 相似文献
19.
Surks HK Mochizuki N Kasai Y Georgescu SP Tang KM Ito M Lincoln TM Mendelsohn ME 《Science (New York, N.Y.)》1999,286(5444):1583-1587
Contraction and relaxation of smooth muscle are regulated by myosin light-chain kinase and myosin phosphatase through phosphorylation and dephosphorylation of myosin light chains. Cyclic guanosine monophosphate (cGMP)-dependent protein kinase Ialpha (cGKIalpha) mediates physiologic relaxation of vascular smooth muscle in response to nitric oxide and cGMP. It is shown here that cGKIalpha is targeted to the smooth muscle cell contractile apparatus by a leucine zipper interaction with the myosin-binding subunit (MBS) of myosin phosphatase. Uncoupling of the cGKIalpha-MBS interaction prevents cGMP-dependent dephosphorylation of myosin light chain, demonstrating that this interaction is essential to the regulation of vascular smooth muscle cell tone. 相似文献
20.
Among the factors that can govern the relative rates of mitochondrial oxidation of isocitrate by means of the isocitrate dehydrogenases linked to diphospho-and triphosphopyridine nucleotides are the intramitochondrial concentrations of these nucleotides. Yeast mitochondria contain enzymes that can alter the ratio of these pyridine nucleotides by interconverting them. A diphosphopyridine nucleotide kinase catalyzes the formation of triphosphopyridine nucleotide from diphosphopyridine nucleotide and adenosine triphosphate; a phosphatase converts triphosphopyridine nucleotide to diphosphopyridine nucleotide. Both reactions are more active with the reduced forms of the pyridine nucleotide coenzymes. These studies suggest that the activity of the mitochondrial triphosphopyridine-nucleotide-linked isocitrate dehydrogenase may be regulated by a cyclic system of pyridine-nucleotide interconversions involving triphosphopyridine nucleotide synthesis and breakdown. 相似文献