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1.
《Phytochemistry》1987,26(3):687-696
To establish structure-activity relationships, 12 mimics of PM-toxin A, a component of the host-specific corn pathotoxin produced by Phyllosticta maydis, have been synthesized as stereoisomeric mixtures. All the mimics synthesized have four β-ketol groups spaced by varying lengths of methylene chains or by a 1,3-diene chain. Mimics with the shorter methylene side-spacers or with the diene side-spacers are 30- to 300-fold less toxic than the native toxin, but the remaining compounds are equally or more toxic than the native toxin. These results can be accounted for by postulating that intramolecular associations at the β-ketol groups may yield two types of cage structure with active and less active conformations. 相似文献
2.
《Insect Biochemistry》1987,17(2):291-301
We have synthesized a tritiated form of 2,14,22,25-tetradeoxyecdysone (5β-ketol) of high specific activity (115 Ci/mmol). We have examined the capacity of various tissues of Locusta migratoria to use this 5β-ketol, a putative precursor of ecdysone, in ecdysteroid biosynthesis. While larval prothoracic glands convert the radiotracer to labelled 14-deoxyecdysone they fail to hydroxylate the molecule to ecdysone itself. Other larval tissues, embryonic tissues or vitellogenic female ovaries are unable to convert the radiotracer to ecdysone, 20-hydroxyecdysone or 2-deoxyecdysone, the terminal products of biosynthesis in different developmental stages. Using subcellular preparations of prothoracic glands or follicle cells we have been unable to show a biological C-14 hydroxylation of 5β-ketol. It thus appears that the step of C-14 hydroxylation in the biosynthesis of ecdysteroids requires a substrate other than 5β-ketol. 相似文献
3.
A novel, site-specific, DNA backbone S-modification (phosphorothioation) has been discovered, but its in vivo function(s) have remained obscure. Here, we report that the enteropathogenic Salmonella enterica serovar Cerro 87, which possesses S-modified DNA, restricts DNA isolated from Escherichia coli, while protecting its own DNA by site-specific phosphorothioation. A cloned 15-kb gene cluster from S. enterica conferred both host-specific restriction and DNA S-modification on E. coli. Mutational analysis of the gene cluster proved unambiguously that the S-modification prevented host-specific restriction specified by the same gene cluster. Restriction activity required three genes in addition to at least four contiguous genes necessary for DNA S-modification. This functional overlap ensures that restriction of heterologous DNA occurs only when the host DNA is protected by phosphorothioation. Meanwhile, this novel type of host-specific restriction and modification system was identified in many diverse bacteria. As in the case of methylation-specific restriction systems, targeted inactivation of this gene cluster should facilitate genetic manipulation of these bacteria, as we demonstrate in Salmonella. 相似文献
4.
J. Gunasingh Masilamoni E. Philip Jesudason S. Dhandayuthapani Ben S. Ashok S. Vignesh W. Charles E. Jebaraj 《Free radical research》2013,47(7):661-673
Widespread cerebral deposition of a 40–42 amino acid peptide called amyloid β peptide (Aβ) in the form of amyloid fibrils is one of the most prominent neuropathologic features of Alzheimer's disease (AD). The clinical study provides evidence that accumulation of protofibrils due to the Arctic mutation (E22G) causes early AD onset. Melatonin showed beneficial effects in an AD mouse model. Mice were divided into four different groups (n=8 per group): (i) control group, (ii) scrambled Aβ-injected group, (iii) Aβ protofibril-injected group and (iv) melatonin-treated group. A single dose of (5 µg) Aβ protofibril was administered to the Aβ protofibril-injected and melatonin-treated groups via intracerebroventricular injections. The results demonstrate that melatonin treatment significantly reduces Aβ protofibril-induced reactive oxygen species (ROS) production, intracellular calcium levels and acetylcholinesterase activity in the neocortex and hippocampus regions. Based on these findings it is suggested that melatonin therapy might be a useful treatment for AD patients. 相似文献
5.
Summary A microscopic assessment is presented of the comparative infection capacity of wild-type and hybrid strains ofRhizobium leguminosarum bv.viciae withR. l. bv.trifolii strain ANU 843 on white clover seedlings. TheR. l. bv.viciae hybrid strains contained defined DNA segments coding for different combinations ofR. l. bv.trifolii host-specific nodulation genes. White clover plants were examined over a 72 h period to assessRhizobium infectivity, the morphological changes in root hair growth; colonisation ability of rhizobia; infection thread initiation and the ability to induce cortical cell division.R. l. bv.viciae strain 300 induced root hair curling more slowly than strain ANU 843 or any of the hybrid strain 300 bacteria, and when curling had taken place, there was poorer colonization by strain 300 within the folded hair cell, no evidence of infection thread formation and only limited cortical cell division 72 h after inoculation. The addition of the host-specific nodulation genes ofR. l. bv.trifolii to strain 300 was necessary to induce infection threads and establish a normal pattern of nodulation of the roots of white clovers. 相似文献
6.
Host-specific Bacteroides–Prevotella 16S rRNA genetic markers are promising alternative indicators for identifying the sources of fecal pollution because of their
high abundance in the feces of warm-blooded animals and high host specificity. However, little is known about the persistence
of these genetic markers in environments after being released into environmental waters. The persistence of feces-derived
four different host-specific Bacteroides–Prevotella 16S rRNA genetic makers (total, human-, cow-, and pig-specific) in environmental waters was therefore investigated at different
incubation temperatures (4, 10, 20, and 30°C) and salinities (0, 10, 20, and 30 ppt) and then compared with the survival of
conventional fecal-indicator organisms. The host-specific genetic markers were monitored by using real-time polymerase chain
reaction (PCR) assays with specific primer sets. Each host-specific genetic marker showed similar responses in non-filtered
river water and seawater: They persisted longer at lower temperatures and higher salinities. In addition, these markers did
not increase in all conditions tested. Decay rates for indicator organisms were lower than those for host-specific genetic
markers at temperature above 10°C. Furthermore, we investigated whether the PCR-detectable 16S rRNA genetic markers reflect
the presence of live target cells or dead target cells in environmental waters. The result revealed that the detection of
the Bacteroides–Prevotella 16S rRNA genetic markers in environmental waters mainly reflected the presence of ‘viable but non-culturable’ Bacteroides–Prevotella cells. These findings indicate that seasonal and geographical variations in persistence of these host-specific Bacteroides–Prevotella 16S rRNA genetic markers must be considered when we use them as alternative fecal indicators in environmental waters. 相似文献
7.
Vichien Kitpreechavanich Mitsunori Hayashi Hidehiko Kumagai Shiro Nagai 《Bioscience, biotechnology, and biochemistry》2013,77(7):1703-1711
A β-xylosidase (β-d-xyloside xylohydrolase, EC 3.2.1.37) and β-glucosidase (β-d-glucoside glucohydrolase, EC 3.2.1.21) extracted from a wheat bran culture of Aspergillus fumigatus were purified up to 90-fold and 131-fold, respectively, by ammonium sulfate precipitation, gel filtration, ion exchange chromatography, and hydroxylapatite chromatography. Molecular weights of the β-xylosidase and β-glucosidase were 360,000 and 380,000, respectively, each consisting of four identical subunits. The isoelectric points of β-xylosidase and β-glucosidase were at pH 5.4 and 4.5, respectively. The optimum temperature for the β-xylosidase was 75°C, being stable up to 65°C for 20 min and for the β-glucosidase was 65°C, being stable up to 60°C for 20 min. The optimum pH for both enzymes was about 4.5, being stable between 2 and 8 at 50°C for 20 min. Both enzymes were inhibited by Fe3+, Cu2+, Hg2+, SDS, and p-chloromercuribenzoate. The apparent Michaelis constants of the β-xylosidase were 2.0 and 23.8 mM for p-nitrophenyl-β-xyloside and xylobiose, respectively, and those of the β-glucosidase were 1.4, 11.4, and 24.8 mM for p-nitrophenyl-β-glucoside, gentiobiose, and cellobiose, respectively. To produce xylose from crude xylooligosac-charides prepared by steam-explosion of cotton seed waste (DP ≤10, 53%, total sugars = 150 g/ liter), the crude enzyme from A. fumigatus (β-xylosidase activity = 14.7 units/ml, xylanase activity = 20 units/ml) could hydrolyze the substrate at 55°C and pH 4.5 resulting in almost complete conversion to xylose (160 g/liter). 相似文献
8.
We found that the gradient of a host-specific attractant, cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone) isolated from the roots of spinach triggered encystment followed by germination of zoospores of Aphanomyces cochlioidesat a concentration less than micromolar order. This compound did not affect the growth and reproduction of this phytopathogen up to 10–6 M concentration in the culture medium. We also observed that mastoparan, an activator of heterotrimeric G-protein could inhibit the motility of zoospores and then strikingly effect encystment followed by 60–80% germination of cysts. Concomitant application of cochliophilin A and mastoparan showed stronger encystment followed by 100% germination of cysts. In addition, we have observed that chemicals interfering with phospholipase C activity (neomycin) and Ca2+ influx/release (EGTA and loperamide) suppress cochliophilin A or mastoparan induced encystment and germination. These results suggest that G-protein mediated signal transduction mechanism may be involved in the differentiation of the A. cochlioides zoospores. This is the first report on the differentiation of oomycete zoospores initiated by a host-specific plant signal or a G-protein activator. 相似文献
9.
AGTG-toxins designated as host-specific toxins were isolated at first from a pathotype of Alternaria alternata attacking Citrus species. A strain of Alternaria alternata isolated from Brassica sinensis in Central Germany and improved to a high tentoxin content, also produces two ACTG-toxins. It is doubtful, therefore, if both substances can be denoted as host-specific toxins. 相似文献
10.
Synthesis and Biological Evaluation of New Natural Phenolic (2E,4E,6E)‐Octa‐2,4,6‐trienoic Esters
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Raffaella Gandolfi Alessandro Contini Daniela Pinto Barbara Marzani Stefano Pandini Donatella Nava Elena Pini 《化学与生物多样性》2017,14(12)
In the present study the esterification of the OH groups of resveratrol, caffeic acid, ferulic acid, and β‐sitosterol with an antioxidant polyconjugated fatty acid, (2E,4E,6E)‐octa‐2,4,6‐trienoic acid, was achieved. As the selective esterification of OH groups of natural compounds can affect their biological activity, a selective esterification of resveratrol and caffeic acid was performed by an enzymatic approach. The new resulting compounds were characterized spectroscopically (FT‐IR, NMR mono, and bidimensional techniques); when necessary the experimental data were integrated by quantum chemical calculations. The antioxidant, anti‐inflammatory and proliferative activity was evaluated. The good results encourage the use of these molecules as antioxidant and/or anti‐inflammatory agents in dermocosmetic application. 相似文献
11.
Summary Differential predation pressure and the probability of predation on a Batesian mimicry complex and on alternative prey were estimatedin a field experiment. The mimicry complex was composed of a noxious model (Eleodes obscura (Say)) and a palatable mimic (Stenomorpha marginata (LeConte)). House crickets (Acheta domesticus) (Linn.) were used as alternative prey. The experiment was conducted for 23 nights in August and September to approximate the peak seasonal activity time period during which both models and mimics normally are exposed to predation while foraging and depositing eggs. Each night thirty prey in ratios of 16 models: 7 mimics: 7 crickets were exposed for 2.5 h to a suite of predators consisting of pallid bats (Antrozous pallidus), striped skunks (Mephitis mephitis) and ringtails (Bassariscus astutus) that had free access to the prey. The model-mimic ratio was similar to that found in nature. Predators obtained prey on 11 of the 23 nights and preferred the alternative prey (crickets) in proportions higher than was expected from a predation rate that was equal on all species of prey. Mimics were taken by predators at a rate proportional to their abundance, while models were taken at a rate considerably lower than their relative abundance. This suggests that at least some of the predators could distinguish between models and mimics and were willing to eat the mimics at higher frequencies than they were willing to eat the models. However, although the mimicry is not perfect with respect to the entire predator suite, the mimics still gain an advantage by resembling the models, compared to the predation levels on the alternate prey. 相似文献
12.
Akihiko Mochizuki Sankichi Horiuchi Nobuichi Goto Rintaro Nakaya 《Microbiology and immunology》1987,31(8):737-744
The plasmid pNR333 is a kanamycin-resistant, deletion derivative of pNR113 with an extremely high copy number in Escherichia coli and in Proteus mirabilis. In order to determine the usefulness of pNR333 as a replication gene of vector, the genes encoding chloramphenicol acetyltransferase (CAT) and β-galactosidase (β-gal) were cloned individually into both pNR333 and other low-copy-number plasmids. The expression of the cloned genes was compared by measuring the specific activity of each enzyme and the amounts of the proteins produced. A hybrid plasmid pNR333-cat expressed 53 times as much activity of CAT as the low-copy plasmid S-a which had a copy number of four. The lacZ gene cloned in pNR333 produced 17 times as much β-gal as in the low-copy-number plasmid pNR1150. These results suggest that pNR333 is a useful vector plasmid for producing a large amount of polypeptides in E. coli hosts. 相似文献
13.
β-galactosidase from E. coli (β-D -galactose galactohydrolase, EC 3.2.1.23) has been entrapped in a crosslinked 2-hydroxyethyl methacrylate gel with a 35% retention of activity. The kinetic behavior of the gel-entrapped enzyme has been studied in a recirculation reactor system, the substrate being o-nitrophenyl-βhyphen;D - galactopyranoside. Kinetic constants were determined for particle sizes ranging from 69 to 231 μm in diameter and compared to those of the free enzyme. External diffusion effects were eliminated by operating at high recirculation flow rates. A fourfold increase in Km(app) was observed for the 231 μm particles, consistent with existing theoretical treatments for internal diffusion effects. An Arrhenius plot of rate data showed significant curvature at higher temperatures, which was attributed to the effects of internal diffusion. The pH–activity profile of the gel-entrapped enzyme was bell-shaped at high substrate concentration and, in contrast to the free enzyme, could be fitted to the titration curve of two ionizable groups, a basic group having a pK of 8.6. The gel-entrapped enzyme had a higher pH optimum and retained a larger percentage of its maximal activity at alkaline pH than the free enzyme; its pH stability at high pH was also much better. The thermal stability of the gel-entrapped enzyme was studied and found to be 14 days at 22°C and 65 min at 45°C. 相似文献
14.
Ronald J. Prokopy Neil W. Miller Jian J. Duan Roger I. Vargas 《Entomologia Experimentalis et Applicata》2000,97(2):211-217
Mature female Mediterranean fruit flies, Ceratitis capitata (Wiedemann), isolated from conspecifics for 7 days prior to testing in laboratory cages, were attracted to yellow plastic fruit-mimicking hemispheres or spheres in significantly greater numbers when groups of conspecific females were present than absent on fruit mimics. Attraction of females to conspecifics occurred for females deprived of protein or continuously provided with protein since eclosion, for fruit mimics that were unbaited or baited with odor of food or fruit, and under single-choice as well as multiple-choice test conditions. Attraction proved just as great to fruit mimics having dead conspecifics as to mimics having live conspecifics, was evident also when fruit mimics were orange or white, and occurred also in response to presence of live Bactrocera dorsalis (Hendel)females on fruit mimics. We discuss our findings in relation to local enhancement, a form of social facilitation in insects and other animals. 相似文献
15.
A variety of organic compounds have been documented to bind to the oestrogen receptor and induce oestrogenic effects in different vertebrates. The presence of these environmental oestrogens or oestrogen mimics in the aquatic environment has been suspected of disrupting the normal endocrinology of wild populations of fish. In this study, induction of vitellogenin synthesis in primary hepatocytes from Atlantic salmon (Salmo salar) was optimized and validated as an oestrogenic in vitro bioassay using a sensitive capture vitellogenin enzyme-linked immunosorbent assay. After proper optimization (cell media supplements, cell density, temperature and exposure time), this assay gave a sensitive and reproducible response to both endogenous steroids (relative potency: 17β-oestradiol?oestriol>oestrone>17α-oestradiol) and a range of common oestrogen mimics (relative potency: ethynyloestradiol and diethylstilboestrol?genistein and zearalenone?bisphenol A and 4-t-octylphenol>4-n-nonylphenol and 2′-chloro,4-chloro-diphenyltrichloroethane (o,p′-DDT). However, the androgen testosterone and the putative oestrogen mimics dieldrin and toxaphene were not shown to be oestrogenic using this hepatocyte bioassay. Oestrogen-induced vitellogenin synthesis was efficiently inhibited by the anti-oestrogen ZM 189.154, suggesting that this bioassay may be used for testing both the oestrogenic and the anti-oestrogenic properties of chemicals. 相似文献
16.
The aim of this study was to assess the effect of the β‐amyloid fragment Aβ25–35 on mitochondrial structure and function and on the expression of proteins associated with the mitochondrial permeability transition pore (MPTP) in rat hippocampal neurons. Ninety clean‐grade Sprague–Dawley rats were randomly assigned to six groups (n = 15 per group). Aβ25–35 (1, 5, or 10 µg/rat) was injected into hippocampal area CA1. Normal saline was injected as a control. The effect of Aβ25–35 injection on hippocampal structure was assessed by transmission electron microscopy. Ca2+‐ATPase activity, [Ca2+]i, and mitochondrial membrane potential were measured. The expression of genes associated with the MPTP, including the voltage‐dependent anion channel (VDAC), adenine nucleotide translocator (ANT), and cyclophilin D (Cyp‐D), were evaluated. Results showed that Aβ25–35 injection damaged the mitochondrial structure of hippocampal neurons, decreased Ca2+‐ATPase activity and mitochondrial membrane potential, and increased [Ca2+]i. The expression levels for VDAC, ANT, and Cyp‐D in all groups were significantly (P < 0.05) higher than those in the normal control group after Aβ25–35 injection. These results indicate that Aβ25–35 damages mitochondria in rat hippocampal neurons and effects mitochondrial dysfunction, as well as increasing the expression of genes associated with the MPTP. Mitochondrial dysfunction may result in increased MPTP gene expression, leading to neurodegenerative effects. J. Cell. Biochem. 112: 1450–1457, 2011. © 2011 Wiley‐Liss, Inc. 相似文献
17.
Deposition of beta‐amyloid (Aβ) is considered as an important early event in the pathogenesis of Alzheimer's Disease (AD), and reduction of Aβ levels by various therapeutic approaches is actively being pursued. A potentially non‐inflammatory approach to facilitate clearance and reduce toxicity is to hydrolyze Aβ at its α‐secretase site. We have previously identified a light chain fragment, mk18, with α‐secretase‐like catalytic activity, producing the 1–16 and 17–40 amino acid fragments of Aβ40 as primary products, although hydrolysis is also observed following other lysine and arginine residues. To improve the specific activity of the recombinant antibody by affinity maturation, we constructed a single chain variable fragment (scFv) library containing a randomized CDR3 heavy chain region. A biotinylated covalently reactive analog mimicking α‐secretase site cleavage was synthesized, immobilized on streptavidin beads, and used to select yeast surface expressed scFvs with increased specificity for Aβ. After two rounds of selection against the analog, yeast cells were individually screened for proteolytic activity towards an internally quenched fluorogenic substrate that contains the α‐secretase site of Aβ. From 750 clones screened, the two clones with the highest increase in proteolytic activity compared to the parent mk18 were selected for further study. Kinetic analyses using purified soluble scFvs showed a 3‐ and 6‐fold increase in catalytic activity (kcat/KM) toward the synthetic Aβ substrate compared to the original scFv primarily due to an expected decrease in KM rather than an increase in kcat. This affinity maturation strategy can be used to select for scFvs with increased catalytic specificity for Aβ. These proteolytic scFvs have potential therapeutic applications for AD by decreasing soluble Aβ levels in vivo. © 2009 American Institute of Chemical Engineers. Biotechnol. Prog., 2009 相似文献
18.
Kiyofumi Sakai Nobutake Hamada Yasuto Watanabe 《Bioscience, biotechnology, and biochemistry》2013,77(4):989-996
The secondary alcohol oxidase from Pseudomonas sp. catalyzed the oxidation of various vinyl alcohol oligomers with the molecular weight of 220 to 1500 and of β-ketols such as 5-hydroxy-3-heptanone, 4-hydroxy-2-nonanone, 3-hydroxy-5-nonanone, 6-hydroxy-4-nonanone, 7-hydroxy-5-dodecanone, and 8-hydroxy-6-tridecanone. β-Diketone hydrolase from the same strain catalyzed the hydrolysis of various aliphatic β-diketones and some aromatic β-diketones such as 1-phenyl-1,3-butanedione and 1-phenyl-2,4-pentanedione. 4,6-Nonanediol, used as a low molecular weight model of poly(vinyl alcohol) (PVA), was oxidized to 4,6-nonanedione by way of 6-hydroxy-4-nonanone by secondary alcohol oxidase. 4,6-Nonanedione was hydrolyzed to 2-pentanone and n-butyric acid by β-diketone hydrolase. These reactions were stoichiometric.The presence of the β-diketone structure in PVA oxidized by secondary alcohol oxidase was confirmed by spectral experiments. The absorption due to β-diketone structure in the oxidized PVA decreased as it was hydrolyzed by β-diketone hydrolase. The ratio of the amount of carboxyl groups in the degraded PVA to that of carbonyl groups in the oxidized PVA became more than 0.5. A pathway for the enzymatic degradation of PVA was proposed. 相似文献
19.
Tomoyoshi Iwatsubo Kiyoshi Sekiguchi Kunio Kurata Tomio Tada Kenji Iki Hiroki Nakagawa 《Bioscience, biotechnology, and biochemistry》2013,77(6):1243-1244
β-Chloro-l-alanine was catalytically converted to pyruvate, ammonia and chloride by α-aminoisobutyrate (AIB) decomposing enzyme (α, β elimination), which was synchronously inactivated. There was a linear relationship between α, β elimination and inactivation. With apoenzyme, neither α, β elimination nor inactivation occurred. These facts suggest that α, β elimination is dependent on pyridoxal 5′-phosphate, and inactivation cooperates with α, β elimination (syncatalytic inactivation). But it seemed that d-form of β-chloroalanine was not a substrate for AIB decomposing enzyme, because just half amount of β-chloro-dl-alanine was decomposed to pyruvate by the enzyme.An identical active site for each of following three reactions were shown by the fact that AIB decomposing activity, transamination activity and α, β elimination activity were lost in parallel. From a kinetic study, the affinity of the enzyme toward β-chloro-l-alanine was shown to be higher than that toward AIB or l-alanine. The turnover number, about 8,000, of α, β elimination during the inactivation of one mol of the enzyme was much larger than that of d-amino acid transaminase or alanine racemase. 相似文献
20.
H. Takahashi K. Takita T. Kishimoto T. Mitsui H. Hori 《Journal of Phytopathology》2002,150(10):529-535
Phenylalanine ammonia‐lyase (PAL, EC 4.3.1.5) activity in clubroot disease‐resistant turnip calli was transiently increased by 20 h after the inoculation with Plasmodiophora brassicae spores. The magnitude of the increase in PAL activity was four to six times higher than constitutive PAL activity. There was no transient increase in PAL activity in susceptible calli. Preincubation of calli in Ca2+‐free medium or the removal of Ca2+ from cell surfaces by ethylene glycol bis(2‐aminoethyl ether)‐N,N,N′,N′‐tetraacetic acid‐chelation, completely inhibited induced PAL activity. The influx of exogenous Ca2+ into cells appears necessary for this pathogen induced PAL activity. Verapamil and the calmodulin inhibitor W7 almost completely inhibited induced PAL activity at 1 and 0.1 mm , respectively. Neomycin, ruthenium red and (1‐(6‐[(17β‐3‐Methoxyestra‐1,3,5‐(10)‐trien‐17‐yl)amino]hexyl)‐1H‐pyrrole‐2,5‐dione) did not inhibit induced PAL activity. Thus, verapamil and N‐(6‐aminohexyl)‐5‐chloro‐1‐naphthalenesulphonamide hydrochloride‐sensitive Ca2+‐mediated signalling process appear necessary for P. brassicae induced PAL activity. As the protein synthesis inhibitor cycloheximide (CHX) blocked the induced increasing PAL activity, de novo synthesis of PAL appears to be required for turnip cell defence reactions against P. brassicae. 相似文献