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101.
M. Schulz M. Bayer H. White H. Gü nther H. Simon 《Biocatalysis and Biotransformation》1994,10(1):25-36
Crude extracts of Clostridium thermoaceticum DSM 521 contain various AMAPORs (artificial mediator accepting pyridine nucleotide oxidoreductases). The specific activities of this mixture of AMAPORs is about 8-9 U mg-1 protein (µmoles mg-1 min-1) for NADPH and 3-4 U mg-1 protein for NADH formation with reduced methylviologen (MV++) as electron donor. These AMAPOR-activities are only slightly oxygen sensitive. The reoxidation of NADPH and NADH with carboxamido-methylviologen is catalysed by crude extracts with 2.0 and 1.6 U mg-1 protein, respectively. The same crude extracts also catalyse the dehydrogenation of reduced pyridine nucleotides with suitable quinones such as anthraquinone-2,6-disulphonate. The reduced quinone can be reoxidised by dioxygen.
The Km-values of these enzymes for the pyridine nucleotides and also for the artificial electron mediators are in a suitable range for preparative transformations.
Furthermore the crude extract of C. thermoaceticum contains about 2.5 U mg-1 protein of an NADP+-dependent formate dehydrogenase (FDH), which is suitable for NADPH and/or MV++ regeneration. The regeneration of MV++ with FDH and formate as electron donor proceeds with a specific activity of about 5 U mg-1 protein of the crude extract. The reduced viologen in turn reduces NAD(P)+ by AMAPOR. The formate dehydrogenase is sensitive to oxygen.
Examples of compounds which have been prepared by combination of AMAPORs or formate dehydrogenase with an oxidoreductase are: (S)-3-hydroxycarboxylates, esters of (S)-3-hydroxycarboxylates, (1R,2S)-1-hydroxypropane-tricarboxylate (Ds-(+)-isocitrate), Ls-(-)-isocitrate and 6-phosphogluconate. 相似文献
The Km-values of these enzymes for the pyridine nucleotides and also for the artificial electron mediators are in a suitable range for preparative transformations.
Furthermore the crude extract of C. thermoaceticum contains about 2.5 U mg-1 protein of an NADP+-dependent formate dehydrogenase (FDH), which is suitable for NADPH and/or MV++ regeneration. The regeneration of MV++ with FDH and formate as electron donor proceeds with a specific activity of about 5 U mg-1 protein of the crude extract. The reduced viologen in turn reduces NAD(P)+ by AMAPOR. The formate dehydrogenase is sensitive to oxygen.
Examples of compounds which have been prepared by combination of AMAPORs or formate dehydrogenase with an oxidoreductase are: (S)-3-hydroxycarboxylates, esters of (S)-3-hydroxycarboxylates, (1R,2S)-1-hydroxypropane-tricarboxylate (Ds-(+)-isocitrate), Ls-(-)-isocitrate and 6-phosphogluconate. 相似文献
102.
Mortimer M. Civan Jonathan Robbins Simon Broad Enrique Rozengurt David A. Brown 《The Journal of membrane biology》1993,133(1):51-59
Summary Differentiated neuroblastoma cells exhibit both the delayed rectifier potassium current (I
K) and the M-current (I
M). The present study was designed to determine the roles of protein kinase C (PKC) and of the calmodulin-binding protein 80K/MARCKS, a prominent substrate for PKC and possible regulator of these currents. Neuroblastoma x glioma (NG108-15) hybrid cells transfected with m1 muscarinic receptors were grown with 1% fetal bovine serum (FBS) without the prostaglandin E1 (PGE1) and isobutylmethylxanthine (IBMX) usually added in preparation for electrophysiological studies. Under these conditions, the usual pleomorphism was largely abolished, leaving two populations of small cells with stellate and spherically symmetrical geometries. Whole-cell patch clamping indicated that the two cell types had identical electrophysiological properties, displaying: I
k, a small current through a T-like Ca2+ channel, and no M-current.Stimulation with carbachol shifted the distribution of cells to a more stellate morphology within 24 hr and later (after 48 hr) reduced the PKC substrate 80K/MARCKS by 22±7%. In contrast to the stimulation of I
k observed with cardiac cells, PKC activation produced only a small inhibition of I
k, which was independent of carbachol pretreatment. Thus, PKC and 80K/MARCKS can be dissociated from the regulation of I
k in neuroblastoma cells.Supported in part by research grants from the National Institutes of Health (DK-40145 and EY-08343) and from the U.K. Medical Research Council.We thank Dr. Peter J. Parker for his generous gift of PKC, and Yvonne Vallis for her skillful assistance with the cultures and harvesting of the NG108-15 transfected cells. 相似文献
103.
Simon Y. C. Wong Geoffrey R. Guile Thomas W. Rademacher Raymond A. Dwek 《Glycoconjugate journal》1993,10(3):227-234
Glycopeptides can be valuable tools in determining the influence of carbohydrate moieties on the intrinsic properties of glycoproteins. However, glycopeptides of sufficient quantity and purity are as yet not readily available from biological sources. The chemical coupling of a -glycosylamino group of an unprotected carbohydrate with an activated aspartic acid residue of an unprotected peptide is a simple method for synthesizing asparagine-linked glycopeptides. In this report we demonstrate that the use of this method is not restricted to -glycosylamines of simple monosaccharides or short aspartic acid-containing pentapeptides. This is illustrated by the syntheses of several glycopentapeptides containingN,N-diacetylchitobiose, a glutamine-linked glycopentapeptide containing a biantennary complex oligosaccharide, and glycosylated variants of two analogs of a polypeptide hormone, atriopeptin, containingN,N-diacetylchitobiose.Abbreviations Ac
acetyl
- Bzl
benzyl
- DMF
dimethylformamide
- Fmoc
9-fluorenylmethoxycarbonyl
- Fuc
fucose
- Gal
galactose
- GlcNAc
N-acetylglucosamine
- HBTU
O-benzotriazol-1-yl-N,N,N,N-tetramethyluroniumhexa-fluorophosphate
- HOBt
1-hydroxybenzotriazole
- Man
mannose
-
m/z
mass/charge
- NMR
nuclear magnetic resonance
- Xyl
xylose
- Z
benzyloxycarbonyl; unless otherwise specified, amino acids are abbreviated using their one-letter codes. 相似文献
104.
The genes of two variant glucoamylases (GLA1 and GLU1) ofSaccharomycopsis fibuligera were expressed inSaccharomyces cerevisiae, and biochemical properties of the secreted enzymes were compared. It was found that three amino acid alterations in the signal peptide and N-terminal regions of the variants had no effect on the levels of the secreted enzymes. Amino acid alterations in the C-terminal region of the mature proteins influenced their specific activity, substrate specificity, as well as temperature and pH optima. Because of the glycosylation heterogeneity, the glucoamylases of each gene variant were isolated and purified in two forms (A and B), which were essentially similar in catalytic and physicochemical properties but differed in their thermal stability and ability to renaturate after thermal denaturation. 相似文献
105.
Anti-Candida activity of four antifungal benzothiazoles 总被引:1,自引:0,他引:1
Helena Bujdáková Tomá Kuchta Eva Sidóová Anna Gvozdjaková 《FEMS microbiology letters》1993,112(3):329-334
Abstract Anti- Candida activity of 6-amino-2- n -pentylthiobenzothiazole (I), benzylester of (6-amino-2-benzothiazolylthio)acetic acid (II) and of 3-butylthio-(1,2,4-triazolo)-2,3-benzothiazole (III) was followed and compared to that of 2-mercaptobenzothiazole (IV). I and II exhibited good activity against the C. albicans yeast form, similar to IV. They were inhibitorily active against other Candida strains, IC50 values being of the order of 10−5 M, which means better activity than IV. Compound I also exhibited inhibitory activity on germ-tube formation and mycelial growth in the C. albicans strains, while II, III and IV were not active in these tests. III was the least active form of the compounds tested, IC50 values being of the order of 10−4 M. All the compounds tested were highly active on a nystatin-resistant C. albicans mutant, with IC50 s of the order of 10−6 M−10−5 M. 相似文献
106.
Simone Prospero Malve Heinz Eva Augustiny Ying-Yu Chen Juanita Engelbrecht Marina Fonti Aliona Hoste Beat Ruffner Romina Sigrist Noelani van den Berg Patrick Fonti 《Environmental microbiology》2023,25(11):2250-2265
Emerging diseases caused by both native and exotic pathogens represent a main threat to forest ecosystems worldwide. The two invasive soilborne pathogens Phytophthora cinnamomi and Phytophthora × cambivora are the causal agents of ink disease, which has been threatening Castanea sativa in Europe for several centuries and seems to be re-emerging in recent years. Here, we investigated the distribution, causal agents, and infection dynamics of ink disease in southern Switzerland. A total of 25 outbreaks were identified, 19 with only P. cinnamomi, 5 with only P. × cambivora, and 1 with both species. Dendrochronological analyses showed that the disease emerged in the last 20–30 years. Infected trees either died rapidly within 5–15 years post-infection or showed a prolonged state of general decline until death. Based on a generalized linear model, the local risk of occurrence of ink disease was increased by an S-SE aspect of the chestnut stand, the presence of a pure chestnut stand, management activities, the proximity of roads and buildings, and increasing annual mean temperature and precipitation. The genetic structure of the local P. cinnamomi population suggests independent introductions and local spread of the pathogen. 相似文献
107.
Laetitia Mathon Virginie Marques Stéphanie Manel Camille Albouy Marco Andrello Emilie Boulanger Julie Deter Régis Hocdé Fabien Leprieur Tom B. Letessier Nicolas Loiseau Eva Maire Alice Valentini Laurent Vigliola Florian Baletaud Sandra Bessudo Tony Dejean Nadia Faure Pierre-Edouard Guerin Meret Jucker Jean-Baptiste Juhel Kadarusman Andrea Polanco F. Laurent Pouyaud Dario Schwörer Kirsten F. Thompson Marc Troussellier Hagi Yulia Sugeha Laure Velez Xiaowei Zhang Wenjun Zhong Loïc Pellissier David Mouillot 《Global Ecology and Biogeography》2023,32(8):1336-1352
Aim
Coastal fishes have a fundamental role in marine ecosystem functioning and contributions to people, but face increasing threats due to climate change, habitat degradation and overexploitation. The extent to which human pressures are impacting coastal fish biodiversity in comparison with geographic and environmental factors at large spatial scale is still under scrutiny. Here, we took advantage of environmental DNA (eDNA) metabarcoding to investigate the relationship between fish biodiversity, including taxonomic and genetic components, and environmental but also socio-economic factors.Location
Tropical, temperate and polar coastal areas.Time period
Present day.Major taxa studied
Marine fishes.Methods
We analysed fish eDNA in 263 stations (samples) in 68 sites distributed across polar, temperate and tropical regions. We modelled the effect of environmental, geographic and socio-economic factors on α- and β-diversity. We then computed the partial effect of each factor on several fish biodiversity components using taxonomic molecular units (MOTU) and genetic sequences. We also investigated the relationship between fish genetic α- and β-diversity measured from our barcodes, and phylogenetic but also functional diversity.Results
We show that fish eDNA MOTU and sequence α- and β-diversity have the strongest correlation with environmental factors on coastal ecosystems worldwide. However, our models also reveal a negative correlation between biodiversity and human dependence on marine ecosystems. In areas with high dependence, diversity of all fish, cryptobenthic fish and large fish MOTUs declined steeply. Finally, we show that a sequence diversity index, accounting for genetic distance between pairs of MOTUs, within and between communities, is a reliable proxy of phylogenetic and functional diversity.Main conclusions
Together, our results demonstrate that short eDNA sequences can be used to assess climate and direct human impacts on marine biodiversity at large scale in the Anthropocene and can further be extended to investigate biodiversity in its phylogenetic and functional dimensions. 相似文献108.
109.
110.
Five insecticide synergists, all of which were either methylenedioxyphenyl compounds or analogs, were compared as to their effect on cytochrome P450 monooxygenase induction caused by an allelochemical in fall armyworm larvae. Feeding the synergists (piperonyl butoxide, safrole, isosafrole, MGK 264, and myristicin) individually to the larvae caused decreases in the microsomal aldrin epoxidase activities ranging from 38% to 74% when compared with controls. Feeding indole-3-carbinol resulted in a 4-fold increase in the microsomal epoxidase activity. However, cotreatment of any of the synergists and the inducer completely eliminated the induction. Sixth instar larvae were more inducible than second instar larvae with respect to microsomal epoxidase and glutathione transferase in the fall armyworm. Enzyme inducibility varied widely among the seven phytophagous Lepidoptera examined. When indole-3-carbinol was used as an inducer of microsomal epoxidase, the extent of inducibility of the enzyme was fall armyworm > velvetbean caterpillar > corn earworm > beet armyworm > tobacco budworm > cabbage looper > diamondback moth. When indole-3-acetonitrile was used as an inducer, the inducibility of glutathione transferase was fall armyworm > beet armyworm > corn earworm > cabbage looper > velvetbean caterpillar > tobacco budworm > diamondback moth. Inducibility of five microsomal oxidase systems also varied considerably in the corn earworm, indicating the multiplicity of cytochrome P450 in this species. Microsomal epoxidase and glutathione transferase were induced by cruciferous host plants such as cabbage and their allelochemicals in diamondback moth larve. © 1993 Wiley-Liss, Inc. 相似文献