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排序方式: 共有622条查询结果,搜索用时 15 毫秒
81.
82.
Matthew Pettengill Simon Robson Megan Tresenriter José Luis Millán Anny Usheva Taiese Bingham Mirjam Belderbos Ilana Bergelson Sarah Burl Beate Kampmann Laura Gelinas Tobias Kollmann Louis Bont Ofer Levy 《The Journal of biological chemistry》2013,288(38):27315-27326
Extracellular adenosine, a key regulator of physiology and immune cell function that is found at elevated levels in neonatal blood, is generated by phosphohydrolysis of adenine nucleotides released from cells and catabolized by deamination to inosine. Generation of adenosine monophosphate (AMP) in blood is driven by cell-associated enzymes, whereas conversion of AMP to adenosine is largely mediated by soluble enzymes. The identities of the enzymes responsible for these activities in whole blood of neonates have been defined in this study and contrasted to adult blood. We demonstrate that soluble 5′-nucleotidase (5′-NT) and alkaline phosphatase (AP) mediate conversion of AMP to adenosine, whereas soluble adenosine deaminase (ADA) catabolizes adenosine to inosine. Newborn blood plasma demonstrates substantially higher adenosine-generating 5′-NT and AP activity and lower adenosine-metabolizing ADA activity than adult plasma. In addition to a role in soluble purine metabolism, abundant AP expressed on the surface of circulating neonatal neutrophils is the dominant AMPase on these cells. Plasma samples from infant observational cohorts reveal a relative plasma ADA deficiency at birth, followed by a gradual maturation of plasma ADA through infancy. The robust adenosine-generating capacity of neonates appears functionally relevant because supplementation with AMP inhibited whereas selective pharmacologic inhibition of 5′-NT enhanced Toll-like receptor-mediated TNF-α production in neonatal whole blood. Overall, we have characterized previously unrecognized age-dependent expression patterns of plasma purine-metabolizing enzymes that result in elevated plasma concentrations of anti-inflammatory adenosine in newborns. Targeted manipulation of purine-metabolizing enzymes may benefit this vulnerable population. 相似文献
83.
84.
Soluble starch synthases and branching enzymes were purified from developing seeds of the maize inbreds W64A and Ia5125, annual teosintes cv. Galinat's Northern Teosinte and race “Nobogame” and diploid perennial teosinte. Two fractions of starch synthase were obtained by DEAE-cellulose chromatography in all purifications. Starch synthase I fractions had citrate stimulated activity and were most active in primed reactions containing glucogen. Starch synthase II fractions were more active in primed reactions with amylopectine and showed no citrate stimulated activity. Three fractions of branching enzymes were similar kinetically and chromatographically. In addition, antibodies prepared against maize branching enzymes cross reacted with teosinte enzymes. Precipitation lines double diffusion experiments and similar neutralizations of enzymes. precipitation lines of identity in double diffusion experiments and similar neutralization of enzyme activity wiyh increasing levels of antiserum, support the conclusion that maize and teosinte enzymes are highly homologous. 相似文献
85.
Sorting nexin 27 interacts with the Cytohesin associated scaffolding protein (CASP) in lymphocytes 总被引:2,自引:0,他引:2
MacNeil AJ Mansour M Pohajdak B 《Biochemical and biophysical research communications》2007,359(4):848-853
CASP is a small cytokine-inducible protein, primarily expressed in hematopoetic cells, which associates with members of the Cytohesin/ARNO family of guanine nucleotide-exchange factors. Cytohesins activate ARFs, a group of GTPases involved in vesicular initiation. Functionally, CASP is an adaptor protein containing a PDZ domain, a coiled-coil, and a potential carboxy terminal PDZ-binding motif that we sought to characterize here. Using GST pulldowns and mass spectrometry we identified the novel interaction of CASP and sorting nexin 27 (SNX27). In lymphocytes, CASP's PDZ-binding motif interacts with the PDZ domain of SNX27. This protein is a unique member of the sorting nexin family of proteins, a group generally involved in the endocytic and intracellular sorting machinery. Endogenous SNX27 and CASP co-localize at the early endosomal compartment in lymphocytes and also in transfection studies. These results suggest that endosomal SNX27 may recruit CASP to orchestrate intracellular trafficking and/or signaling complexes. 相似文献
86.
Tahara T Tanaka M Nozaki S Jin G Onoe H Watanabe Y 《Biochemical and biophysical research communications》2007,353(4):1068-1073
Fatigue can be defined physiologically as inability to maintain the expected power output. At present, no standard of fatigue are yet available. In order to find biomarkers of fatigue, we investigated the level of delta-aminolevulinic acid (ALA), the first intermediate metabolite in the heme biosynthetic pathway, in the plasma and urine of an animal model of fatigue. To prepare fatigued animals, we kept rats for 5 days in a cage filled with water to a height of 1.5 cm. As a result, the plasma and urinary ALA levels were increased in the fatigued animals as compared with those in the control animals. One day after the rats had been returned to their normal cages, these increased levels were restored to the control ones. We also examined the activity of the enzyme ALA dehydratase (ALAD), which is the second enzyme in the heme biosynthetic pathway, and ALAD gene expression during the fatigue and its recovery sessions. The ALAD activity, as well as its gene expression, in the liver of the fatigued animals was decreased as compared with those of the control animals. Both activity and gene expression of ALAD were recovered to their respective control levels after the rats had been allowed to rest in their normal cages for 1 day. Furthermore, the activity of ALA synthase (ALAS), the rate-limiting enzyme in the heme biosynthesis, in the liver was increased after the fatigue session for 5 days. Although this level of increase in the plasma concentration of ALA may not induce fatigue, increase in plasma and urinary ALA levels can be biomarkers of fatigue. 相似文献
87.
Purification and characterization of an ADP-dependent phosphofructokinase from Thermococcus zilligii 总被引:1,自引:0,他引:1
R. S. Ronimus Jurre Koning H. W. Morgan 《Extremophiles : life under extreme conditions》1999,3(2):121-129
The ADP-dependent phosphofructokinase (PFK) from Thermococcus zilligii has been purified 950 fold; it had a specific activity of 190 U mg−1. The enzyme required Mg2+ ions for optimal activity and was specific for ADP. The forward reaction kinetics were hyperbolic for both cosubstrates (pH
optimum of 6.4), and the apparent K
m values for ADP and fructose-6-phosphate were 0.6 mM (apparent V
max of 243 U mg−1) and 1.47 mM (apparent V
max of 197 U mg−1), respectively. Significantly, the enzyme is indicated to be nonallosteric but was slightly activated by some monovalent
cations including Na+ and K+. The protein had a subunit size of 42.2 kDa and an estimated native molecular weight of 66 kDa (gel filtration). Maximal
reaction rates for the reverse reaction were attained at pH 7.5–8.0, and the apparent K
m values for fructose-1,6-bisphosphate and AMP were 0.56 mM (apparent V
max of 2.9 U mg−1) and 12.5 mM, respectively. The biochemical characteristics of this unique ADP-dependent enzymatic activity are compared
to ATP and pyrophosphate-dependent phosphofructokinases.
Received: August 14, 1998 / Accepted: December 2, 1998 相似文献
88.
Sulfite-oxidizing enzyme activities were analyzed in cell-free extracts of aerobically grown cells of Acidianus ambivalens, an extremely thermophilic and chemolithoautotrophic archaeon. In the membrane and cytoplasmic fractions, two distinct enzyme
activities were found. In the membrane fraction, a sulfite:acceptor oxidoreductase activity was found [530 mU (mg protein)–1; apparent K
m for sulfite, 3.6 mM]. In the cytoplasmic fraction the following enzyme activities were found and are indicative of an oxidative
adenylylsulfate pathway: adenylylsulfate reductase [138 mU (mg protein)–1], adenylylsulfate:phosphate adenyltransferase [“ADP sulfurylase”; 86 mU (mg protein)–1], adenylate kinase [650 mU (mg protein)–1], and rhodanese [thiosulfate sulfur transferase, 9.2 mU (mg protein)–1]. In addition, 5′,5′′′-P1,P4-di(adenosine-5′) tetraphosphate (Ap4A) synthase and Ap4A pyrophosphohydrolase activities were detected.
Received: 17 August 1998 / Accepted: 29 April 1999 相似文献
89.
Luiz Antonio Dutra Jéssica Frade O. Guanaes Nadine Johmann Maria Elisa Lopes Pires Chung Man Chin Sisi Marcondes Jean Leandro Dos Santos 《Bioorganic & medicinal chemistry letters》2017,27(11):2450-2453
Resveratrol (RVT) is a stilbene with a protective effect on the cardiovascular system; however, drawbacks including low bioavailability and fast metabolism limit its efficacy. In this work we described new resveratrol derivatives with nitric oxide (NO) release properties, ability to inhibit platelet aggregation and in vivo antithrombotic effect. Compounds (4a–f) were able to release NO in vitro, at levels ranging from 24.1% to 27.4%. All compounds (2a–f and 4a–f) have exhibited platelet aggregation inhibition using as agonists ADP, collagen and arachidonic acid. The most active compound (4f) showed reduced bleeding time compared to acetylsalicylic acid (ASA) and protected up to 80% against in vivo thromboembolic events. These findings suggest that hybrid resveratrol-furoxan (4f) is a novel lead compound able to prevent platelet aggregation and thromboembolic events. 相似文献