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1.
J. Hlaváček J. Pícha V. Vaněk J. Jiráček J. Slaninová V. Fučík M. Buděšínský D. Gilner R. C. Holz 《Amino acids》2010,38(4):1155-1164
A series of N
α-acyl (alkyl)- and N
α-alkoxycarbonyl-derivatives of l- and d-ornithine were prepared, characterized, and analyzed for their potency toward the bacterial enzyme N
α-acetyl-l-ornithine deacetylase (ArgE). ArgE catalyzes the conversion of N
α-acetyl-l-ornithine to l-ornithine in the fifth step of the biosynthetic pathway for arginine, a necessary step for bacterial growth. Most of the
compounds tested provided IC50 values in the μM range toward ArgE, indicating that they are moderately strong inhibitors. N
α-chloroacetyl-l-ornithine (1g) was the best inhibitor tested toward ArgE providing an IC50 value of 85 μM while N
α-trifluoroacetyl-l-ornithine (1f), N
α-ethoxycarbonyl-l-ornithine (2b), and N
α-acetyl-d-ornithine (1a) weakly inhibited ArgE activity providing IC50 values between 200 and 410 μM. Weak inhibitory potency toward Bacillus subtilis-168 for N
α-acetyl-d-ornithine (1a) and N
α-fluoro- (1f), N
α-chloro- (1g), N
α-dichloro- (1h), and N
α-trichloroacetyl-ornithine (1i) was also observed. These data correlate well with the IC50 values determined for ArgE, suggesting that these compounds might be capable of getting across the cell membrane and that
ArgE is likely the bacterial enzymatic target. 相似文献
2.
Detergent solubilization and hydrophobic chromatography of rat brain phosphatidylinositol kinase 总被引:4,自引:0,他引:4
Rat brain microsomal phosphatidylinositol kinase activity was maximally activated in the presence of either 3 mM sodium deoxycholate, 2% Triton-X-100, or 30–40 mM octylglucoside. Among these detergents, 1% Triton-X-100 was most effective in solubilizing the enzyme, and after treatment with, this agent, 100% of the activity was recovered in the high speed supernatant. Octylglucoside solubilized 40% of the enzyme at concentrations below its critical micelle concentration of 25 mM and up to 80% at higher levels. Solubilized phosphatidylinositol kinase failed to adsorb to adenosine nucleotide affinity resins. However, when the Triton-X-100 extract was chromatographed on an uncharged hydrophobic resin, consisting of dodecyl chains attached to Sepharose 4B by ether bonds, nearly all the enzyme activity was retained, and from 44–85% could be eluted with 8 mM sodium deoxycholate. Solubilization followed by hydrophobic chromatography resulted in several-fold purification of phosphatidylinositol kinase and may have disrupted interactions of the enzyme with other hydrophobic proteins sufficiently to allow its substantial purification by conventional or affinity chromatography techniques.The abbreviations used are phosphatidylinositol
1,2-diacyl-sn-glycero-3-phosphoryl-1-l-myo-inositol
- phosphatidylinositolphosphate
1,2-diacyl-sn-glycero-3-phosphoryl-1-l-myo-inositol-4-monophosphate
- phosphatidylinositolbisphosphate
1,2-diacyl-sn-glycerol-3-phosphoryl-1-l-myo-inositol-4,5-bisphosphate
- octylglucoside
1-0-n-octyl-d-glucopyranoside 相似文献
3.
Perturbation of DPPC bilayers by high concentrations of pulmonary surfactant protein SP-B 总被引:3,自引:0,他引:3
Deuterium (2H) NMR has been used to observe perturbation of dipalmitoylphosphatidylcholine (DPPC) bilayers by the pulmonary surfactant protein B (SP-B) at concentrations up to 17% (w/w). Previous 2H NMR studies of DPPC/dipalmitoylphosphatidylglycerol (DPPG) (7:3) bilayers containing up to 11% (w/w) SP-B and DPPC bilayers containing up to 11% (w/w) synthetic SP-B indicated a slight effect on bilayer chain order and a more substantial effect on motions that contribute to decay of quadrupole echoes obtained from bilayers of deuterated DPPC. This is consistent with the perturbation of headgroup-deuterated DPPC reported here for bilayers containing 6 and 9% (w/w) SP-B. For the higher concentrations of SP-B investigated in the present work, 2H NMR spectra of DPPC deuterated in both the headgroup and chain display a prominent narrow component consistent with fast, large amplitude reorientation of some labeled lipid. Similar spectral perturbations have been reported for bilayers in the presence of the antibiotic polypeptide nisin. The observation of large amplitude lipid reorientation at high SP-B concentration could indicate that SP-B can induce regions of high bilayer curvature and thus provides some insight into local interaction of SP-B with DPPC. Such local interactions may be relevant to the formation, in vitro and in vivo, of tubular myelin, a unique structure found in extracellular pulmonary surfactant, and to the delivery of surfactant material to films at the air–water interface.Abbreviations DPPC 1,2-dipalmitoyl-sn-glycero-3-phosphocholine - DPPG 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol - DPPC-d62 1,2-perdeuterodipalmitoyl-sn-glycero-3-phosphocholine - DPPC-d4 1,2-dipalmitoyl-sn-glycero-3-phospho-(, perdeutero)-choline 相似文献
4.
Summary Peroxidase-labelled lectins specific for various carbohydrate residues were used as histochemical reagents in the investigation of Hurler's syndrome. Peanut lectin was used to detect terminald-galactose, wheatgerm lectin forN-acetyl-d-glucosamine, soybean lectin forN-acetyl-d-galactosamine,Tetragonolobus lotus lectin for -l-fucose andBandeiraea S. lectin for -d-galactose. It was found that Kupffer cells in the liver and splenic reticulo-endothelial cells contain acid mucopolysaccharides which bind lectins in paraffin sections after appropriate fixation. The pattern of lectin binding suggests that such cells contain significant amounts ofd-galactose,l-fucose,N-acetyl-d-galactosamine andN-acetyl-d-glucosamine. It is likely that the last named carbohydrate is present as a polymer. Neurones contain a different carbohydrate, rich in galactose and fucose but poor inN-acetyl-d-glucosamine. This compound is resistant to lipid extraction. Hepatocytes, as a rule, do not react with lectins, most likely because of loss of the more soluble mucopolysaccharides during fixation. The results are consistent with the biochemical data of Hurler's syndrome and indicate that lectins can be a useful tool for the investigation of the cytochemistry of storage disorders. 相似文献
5.
Mariachiara Conte Francesco Aliberti Laura Fucci Marina Piscopo 《World journal of microbiology & biotechnology》2007,23(12):1679-1683
Antibacterial effects of various arginine- and lysine-rich polycationic proteins and polymers were evaluated by broth and
solid dilution assay on a range of foodborne pathogens, Gram-positive and Gram-negative bacteria. The Minimum Inhibitory Concentration
(MIC) and the Minimum Bactericidal Concentration (MBC) of α-poly-l-lysine (poly-lys), α-poly-l-arginine (poly-arg) and protamines from herring sperm (clupeine sulphate) and salmon sperm (salmine sulphate) were determined
on Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium, Shigella sonnei,
Escherichia coli O157:H7 and Pseudomonas aeruginosa. All these molecules showed antibacterial activity on all strains with different MIC and MBC values. The molecular mechanisms
underlying the effect of α-poly-l-arginine might be related to the entrance of the molecule into the cell. In fact α-poly-l-arginine labelled with 7-Diethylamino coumarin-3-carboxylic acid, succinimidyl ester (DEAC,SE) showed ability to permeate
the cell membrane of B. cereus and E. coli O157:H7. 相似文献
6.
Xinying Jia Kiyoshi Ozawa Karin Loscha Gottfried Otting 《Journal of biomolecular NMR》2009,44(2):59-67
Cell-free protein synthesis provides rapid and economical access to selectively 15N-labelled proteins, greatly facilitating the assignment of 15N-HSQC spectra. While the best yields are usually obtained with buffers containing high concentrations of potassium l-glutamate, preparation of selectively 15N-Glu labelled samples requires non-standard conditions. Among many compounds tested to replace the l-Glu buffer, potassium N-acetyl-l-glutamate and potassium glutarate were found to perform best, delivering high yields for all proteins tested, with preserved
selectivity of 15N-Glu labelling. Assessment of amino-transferase activity by combinatorial 15N-labelling revealed that glutarate and N-acetyl-l-glutamate suppress the transfer of the 15N-α-amino groups between amino acids less well than the conventional l-Glu buffer. On balance, the glutarate buffer appears most suitable for the preparation of samples containing 15N-l-Glu while the conventional l-Glu buffer is advantageous for all other samples.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
7.
S. Østergaard H. B. Aa. Theilgaard J. Nielsen 《Applied microbiology and biotechnology》1998,50(6):663-668
We have demonstrated that Penicillium chrysogenum possesses the l-cysteine biosynthetic enzyme O-acetyl-l-serine sulphhydrylase (EC 4.2.99.8) of the direct sulphhydrylation pathway. The finding of this enzyme, and thus the presence
of the direct sulphhydrylation pathway in P. chrysogenum, creates the potential for increasing the overall yield in penicillin production by enhancing the enzymatic activity of this
microorganism. Only O-acetyl-l-serine sulphhydrylase and O-acetyl-l-homoserine sulphhydrylase (EC 4.2.99.10) have been demonstrated to use O-acetyl-l-serine as substrate for the formation of l-cysteine. The purified␣enzyme did not catalyse the formation of l-homocysteine from O-acetyl-l-homoserine and sulphide, excluding the possibility that the purified enzyme was O-acetyl-l-homoserine sulphhydrylase with multiple substrate specificity. The purification enhanced the enzymatic specific activity
93-fold in relation to the cell-free extract. Two bands, showing exactly the same intensity, were present on a sodium dodecyl
sulphate/polyacrylamide gel, and the molecular masses of these were estimated to be 59 kDa and 68 kDa respectively. The K
m value for O-acetyl-l-serine and V
max of O-acetyl-l-serine sulphhydrylase were estimated to be 1.3 mM and 14.9 μmol/mg protein−1 h−1 respectively. The activity of the purified enzyme had a temperature optimum of approximately 45 °C, which is much higher
than the actual temperature for penicillin synthesis. Furthermore, O-acetyl-l-serine sulphhydrylase activity was to have a maximum in the range of pH 7.0–7.4.
Received: 20 March 1998 / Received revision: 27 July 1998 / Accepted: 12 August 1998 相似文献
8.
Hong E Larios F Gómez-Viquez NL Huang F Bravo G 《Journal of physiology and biochemistry》2011,67(3):427-435
The contribution of α-adrenoceptors and nitric oxide (NO) on the alterations of sympathetically mediated cardiovascular responses
after acute (AcH) and chronic (ChH) hypertension was evaluated in pithed aortic coarcted hypertensive rats. Pressor and tachycardia
response produced by electrical stimulation of preganglionic sympathetic fibers or exogenous noradrenaline (NA) were recorded
in the absence and presence of prazosin (α1-antagonist), rauwolscine (α2-antagonist), or N
G-nitro-l-arginine methyl ester (l-NAME; an inhibitor of NO synthase). Compared with age-matched sham-operated rats (Nt), the pressor response produced by electrical
stimulation or NA was smaller in AcH rats and larger in ChH rats. Prazosin caused a decrease of pressor response elicited
by electrical stimulation or NA in all groups. However, this effect was higher in ChH. Rauwolscine produced a similar increase
of sympathetically mediated pressor response in Nt and AcH rats. Nevertheless, this antagonist did not affect the sympathetically
mediated pressor response in ChH rats. In addition, rauwolscine did not affect the NA-induced pressor response in all groups.
The pressor response elicited by l-NAME was larger in all groups compared without l-NAME and in presence of l-arginine. Moreover, l-NAME in the presence of NA increased sympathetically mediated pressor response is in all groups, compared without it or in
the presence of l-arginine. Compared with Nt, basally produced NO in aortic rings was increased in AcH but decreased in ChH. Collectively,
our data suggest that decreased cardiovascular reactivity in AcH is due to an increase in basally produced NO. In ChH, enhanced
cardiovascular response appears to be associated with a decrease in produced NO and an increase in released NA from sympathetic
nerves. 相似文献
9.
To efficiently produce xylobiose from xylan, high-level expression of an α-l-arabinofuranosidase gene from Thermotoga maritima was carried out in Escherichia coli. A 1.5-kb DNA fragment, coding for an α-l-arabinofuranosidase of T. maritima, was inserted into plasmid pET-20b without the pelB signal sequence leader, and produced pET-20b-araA1 with 8 nt spacing between ATG and Shine–Dalgarno sequence. A maximum activity of 12 U mg−1 was obtained from cellular extract of E. coli BL21-CodonPlus (DE3)-RIL harboring pET-20b-araA1. The over-expressed α-l-arabinofuranosidase was purified 13-fold with a 94% yield from the cellular extract of E. coli by a simple heat treatment. Production of xylooligosaccharides from corncob xylan by endoxylanase and α-l-arabinofuranosidase was examined by TLC and HPLC: xylobiose was the major product from xylan at 90 °C and its proportion
in the xylan hydrolyzates increased with the reaction time. Hydrolysis with in the xylanase absence of α-l-arabinofuranosidase gave only half this yield.
Revisions requested 27 October 2005; Revisions received 5 September 2005 相似文献
10.
Purification and properties of thermostable N-acylamino acid racemase from Amycolatopsis sp. TS-1-60
Thermostable N-acylamino acid recemase from Amycolatopsis sp. TS-1-60, a rare actinomycete strain selected for its ability to grow on agar plates incubated at 40° C, was purified to homogeneity and characterized. The relative molecular mass (M
r) of the native enzyme and the subunit was estimated to be 300 000 and 40 000 on gel filtration chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis respectively. The isoelectric point (pI) of the enzyme was 4.2. The optimum temperature and pH were 50° C and 7.5 respectively. The enzyme was stable at 55° C for 30 min. The enzyme catalyzed the racemization of optically active N-acylamino acids such as N-acetyl-l-or d-methionine, N-acetyl-l-valine, N-acetyl-l-tyrosine and N-chloroacetyl-l-valine. In addition, the enzyme also catalyzed the recemization of the dipeptide l-alanyl-l-methionine. By contrast, the optically active amino acids, N-alkyl-amino acids and methyl and athyl ester derivatives of N-acetyl-d- and l-methionine were not racemized. The apparent K
m values for N-acetyl-l-methionine and N-acetyl-d-methionine were calculated to be 18.5 mM and 11.3 mM respectively. The enzyme activity was markedly enhanced by the addition of divalent metal ions such as Co2+, Mn2+ and Fe2+ and was inhibited by addition of EDTA and P-chloromercuribenzoic acid. The similarity between the NH2-terminal amino acid sequence of the enzyme and that of Streptomyces atratus Y-53 [Tokuyama et al. (1994) Appl Microbiol Biotechnol 40:835–840] was above 80%. 相似文献
11.
Bach T. Dinh Mohamad N. Zanbrakji Kevin Dove Stacy E. Price Marit Peterson Keith M. Davies 《Nitric oxide》2008,19(4):326-332
Thiolysis of the model diazeniumdiolate prodrug, O2-(2,4-dinitrophenyl) 1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DNP-DEA/NO, 1), by glutathione (GSH), cysteine (CYSH) and 1-heptanethiol (heptylmercaptan, HM) has been examined in anionic (DOPG), neutral (DPPC, DOPE) and cationic (DOTAP) vesicle media and in glycine buffered aqueous solutions. DOTAP vesicles accelerate the bimolecular reaction with glutathione, cysteine and 1-heptanethiol by factors of 81, 8.2 and 4630, respectively, while reaction is inhibited 5- to 10-fold in the presence of neutral and anionic vesicles. The intrinsic nucleophilicity of the thiols has been compared through the second-order rate constants, 22.9, 5.24 and 43.1 M−1 s−1, for nucleophilic attack on 1 by GS−, CYS− and M−, respectively, obtained in buffered aqueous media. Analysis of the catalysis by DOTAP vesicles, using pseudophase ion-exchange formalism, suggests that the rate increase is due to reactant concentration in the bilayer and interfacial region coupled with enhanced dissociation of the thiol at the vesicle surface. Some contribution from enhanced nucleophilic reactivity at the vesicle interface may also contribute to the greater catalysis by HM. Inhibition of the thiolysis reaction by phospholipid liposomes is attributed to repulsion of the thiolate anions by the negatively charged acyl phosphate of the lipid head group. DOPG = 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)], DPPC = 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, DOPE = 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine, DOTAP = 1,2-dioleoyl-3-trimethylammonium-propane. 相似文献
12.
Evidence for NO-dependent vasodilation in the trout (Oncorhynchus mykiss ) coronary system 总被引:1,自引:0,他引:1
T. Mustafa C. Agnisola J. K. Hansen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):98-104
The effects of l-arginine, and its analogues N
ω-nitro-l-arginine methyl ester and N
ω-nitro-l-arginine on vascular resistance were investigated in the intact coronary system of an isolated non-working trout heart preparation.
l-Arginine, at 10–8 mol · l–1induced a slight vasodilatory effect (max 10%). N
ω-nitro-l-arginine methyl ester and N
ω-Nitro-l-arginine in the range 10–8–10–4 mol · l–1 caused dose-dependent increases in coronary resistance. The vasodilatory action of l-arginine was abolished when the preparation was pretreated with 10–4 mol · l–1
N
ω-nitro-l-arginine or N
ω-nitro-l-arginine methyl ester. Nitroprusside alone at 1 mmol · l–1 induced a maximum vasodilation (30%) of the coronary system. Methylene blue a known inhibitor of guanylate cyclase, induced
a strong vasoconstriction (already significant at 10–5 mol · l–1) and was able to overcome the vasodilative effect of nitroprusside. The endothelial nitric oxide agonists acetylcholine and
serotonin, established in mammalian vessels, also mediate vasodilation in trout coronary system. In 50% of preparations, acetylcholine
induced a biphasic response with vasodilation at low concentration (max 15% at 10–8 mol · l–1). Serotonin displayed a dose-response vasodilation in the range 10–8–10–4 mol · l–1 (max 20%). These vasodilative effects were reduced or abolished by 10–4 mol · l–1
l-NA. These data support the existence of NO-mediated vasodilation mechanisms in the trout coronary system.
Accepted: 1 July 1996 相似文献
13.
Koseki T Mese Y Nishibori N Masaki K Fujii T Handa T Yamane Y Shiono Y Murayama T Iefuji H 《Applied microbiology and biotechnology》2008,80(6):1007-1013
An α-l-rhamnosidase was purified by fractionating a culture filtrate of Aspergillus kawachii grown on l-rhamnose as the sole carbon source. The α-l-rhamnosidase had a molecular mass of 90 kDa and a high degree of N-glycosylation of approximately 22%. The enzyme exhibited optimal activity at pH 4.0 and temperature of 50 °C. Further, it
was observed to be thermostable, and it retained more than 80% of its original activity following incubation at 60 °C for
1 h. Its T
50 value was determined to be 72 °C. The enzyme was able to hydrolyze α-1,2- and α-1,6-glycosidic bonds. The specific activity
of the enzyme was higher toward naringin than toward hesperidin. The A. kawachii α-l-rhamnosidase-encoding gene (Ak-rhaA) codes for a 655-amino-acid protein. Based on the amino acid sequence deduced from the cDNA, the protein possessed 13 potential
N-glycosylation recognition sites and exhibited a high degree of sequence identity (up to 75%) with the α-l-rhamnosidases belonging to the glycoside hydrolase family 78 from Aspergillus aculeatus and with hypothetical Aspergillus oryzae and Aspergillus fumigatus proteins.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
14.
An DS Cui CH Sung BH Yang HC Kim SC Lee ST Im WT Kim SG 《Applied microbiology and biotechnology》2012,94(3):673-682
The gene encoding an α-l-arabinofuranosidase that could biotransform ginsenoside Rc {3-O-[β-d-glucopyranosyl-(1–2)-β-d-glucopyranosyl]-20-O-[α-l-arabinofuranosyl-(1–6)-β-d-glucopyranosyl]-20(S)-protopanaxadiol} to ginsenoside Rd {3-O-[β-d-glucopyranosyl-(1–2)-β-d-glucopyranosyl]-20-O-β-d-glucopyranosyl-20(S)-protopanaxadiol} was cloned from a soil bacterium, Rhodanobacter ginsenosidimutans strain Gsoil 3054T, and the recombinant enzyme was characterized. The enzyme (AbfA) hydrolyzed the arabinofuranosyl moiety from ginsenoside
Rc and was classified as a family 51 glycoside hydrolase based on amino acid sequence analysis. Recombinant AbfA expressed
in Escherichia coli hydrolyzed non-reducing arabinofuranoside moieties with apparent K
m values of 0.53 ± 0.07 and 0.30 ± 0.07 mM and V
max values of 27.1 ± 1.7 and 49.6 ± 4.1 μmol min−1 mg−1 of protein for p-nitrophenyl-α-l-arabinofuranoside and ginsenoside Rc, respectively. The enzyme exhibited preferential substrate specificity of the exo-type
mode of action towards polyarabinosides or oligoarabinosides. AbfA demonstrated substrate-specific activity for the bioconversion
of ginsenosides, as it hydrolyzed only arabinofuranoside moieties from ginsenoside Rc and its derivatives, and not other sugar
groups. These results are the first report of a glycoside hydrolase family 51 α-l-arabinofuranosidase that can transform ginsenoside Rc to Rd. 相似文献
15.
Jian-Qiang Fan Long H. Huynh Bruce B. Reinhold Vernon N. Reinhold Kaoru Takegawa Shojiro Iwahara Akihiro Kondo Ikunoshin Kato Yuan C. Lee 《Glycoconjugate journal》1996,13(4):643-652
We have reported that transglycosylation activity of endo--N-acetylglucosaminidase fromArthrobacter protophormiae (endo-A) can be enhanced to near completion using GlcNAc as an acceptor in a medium containing 30% acetone (Fan J-Q, Takegawa K, Iwahara S, Kondo A, Kato I, Abeygunawardana C, Lee YC (1995)J Biol Chem
270: 17723–29). In this paper, we found that the endo-A can also transfer an oligosaccharide, Man9GlcNAc, tol-Fuc using Man9GlcNAc2Asn as donor substrate in a medium containing 35% acetone. The transglycosylation yield was greater than 25% when 0.2m l-Fuc was used as acceptor. The transglycosylation product was purified by high performance liquid chromatography on a graphitized carbon column and the presence ofl-Fuc was confirmed by sugar composition analysis and electrospray mass spectrometry. Sequential exo-glycosidase digestion of pyridyl-2-aminated transglycosylation product, Man9GlcNAc-l-Fuc-PA, revealed that a -anomeric configuration linkage was formed between GlcNAc andl-Fuc. The GlcNAc was found to be 1,2-linked tol-Fuc by two methods; i) collision-induced decomposition on electrospray mass spectrometry after periodate oxidation, reduction and permethylation of Man9GlcNAc-l-Fuc; and ii) preparation of Man9GlcNAc-l-Fuc-PA, its periodate oxidation and reduction, followed by hydrolysis and HPLC analysis. Thus, the structure of the oligosaccharide synthesized by endo-A transglycosylation was determined to be Man9GlcNAc(1,2)-l-Fuc. Methyl -l-fucopyranoside,l-Gal are also acceptors for the enzymic transglycosylation. However, transglycosylation failed when methyl -l-fucopyranoside,d-Fuc andd-Gal were used. These results indicate that the endo-A requires not only 3-OH and 4-OH to be equatorial but also a4C1-conformation or equivalent conformation of the acceptor to perform transglycosylation.Abbreviations endo-A
endo--N-acetylglucosaminidase fromArthrobacter protophormiae
- PA
pyridyl-2-amino-
- AP
aminopyridine
- GlcNAc
N-acetyl-d-glucosamine
- Man
mannose
- Gal
galactose
- Fuc
fucose
- Glc
glucose
- PA-C2
PA-glycolaldehyde
- PA-C3
PA-l-glyceraldehyde
- PA-C4
PA-d-threose
- HPAEC-PAD
high performance anion exchange chromatography with pulsed amperometric detector
- HPLC
high performance liquid chromatography
- ODS
octadecylsilyl
- ES-MS
electrospray mass spectrometry
- CID
collision-induced decomposition 相似文献
16.
Taste cells are specialized epithelial cells that respond to stimulation with release of neurotransmitters onto afferent nerves
that innervate taste buds. In analogy to neurotransmitter release in other cells, it is expected that neurotransmitter release
in taste cells is dependent on an increase in intracellular Ca2+ ([Ca2+]
i
). We have studied changes in [Ca2+]
i
elicited by the taste stimuli l- and d-arginine in isolated taste cells from the channel catfish (Ictalurus punctatus). In a sample of 119 cells, we found 15 cells responding to l-arginine, and 12 cells responding to d-arginine with an increase in [Ca2+]
i
. The response to l-arginine was inhibited by equimolar d-arginine in cells where d-arginine alone did not cause a change in [Ca2+]
i
, which is consistent with mediation of this response by a previously characterized l-arginine-gated nonspecific cation channel antagonized by d-arginine [31]. However, we also found that these taste stimuli elicited decreases in [Ca2+]
i
in substantial number of cells (6 for l-Arg, and 2 for d-Arg, n= 119). These observations suggest that stimulation of taste cells with sapid stimuli may result in simultaneous excitation
and inhibition of different taste cells within the taste bud, which could be involved in local processing of the taste signal.
Received: 25 May 1995/Revised: 29 September 1995 相似文献
17.
Chemical structure and quality of agars from Gracilaria 总被引:3,自引:0,他引:3
Erminio Murano 《Journal of applied phycology》1995,7(3):245-254
Agar polymers synthesized by species of the genus Gracilaria constitute a complex mixture of molecules, containing several extremes in structure. Sulphate hemi-esters, methyl ethers
and pyruvic ketals can alter in a number of ways the structural regularity of agar based on strictly 3-O-linked β-l-galactopyranose and 4-O-linked α-l-galactopyranose residues. In comparison with agars from Gelidium and Pterocladia, agars from Gracilaria can have higher degrees of sulphation, methoxylation and pyruvylation. The gelling ability of agars from most of Gracilaria species is considerably improved by adopting, before extraction, an alkali pretreatment which converts α-l-galactose 6 sulphate into 3,6-anhydro-α-l-galactose. Native agars obtained from Gracilaria cannot be classified, with few exceptions, as bacteriological grade agar as they have a high content of methoxyls and consequently
high gelling temperatures. On the contrary, the genus Gracilaria is considered the most important source of food and sugar-reactive grade agars.
Among techniques which can be used to study algal polysaccharides, combined 1H and 13C nuclear magnetic resonance spectroscopy represent the most effective and powerful method for the investigation of the chemical
structure of agarocolloids. 相似文献
18.
In humans, the quantity of α-l-fucosidase in serum is determined by heredity. The mechanism controlling levels of the enzyme in serum is unknown. Lymphoid
cell lines derived from individuals with either low, intermediate, or high α-l-fucosidase in serum were established. Steady-state levels of intracellular and extracellular α-l-fucosidase as well as rates of synthesis and secretion of enzyme overlapped among the cell lines. Thus,vivo} serum phenotypes were not expressed in this system. No appreciable differences in the qualitative processing of newly made
α-l-fucosidase were observed among these lymphoid cell lines. Cells pulse-labeled with35S-methionine from 0.25 to 2 hr had an intracellular form of enzyme with aM
r=58,000. Cells pulsed for 1.5 hr and chased for 21 hr with unlabeled methionine had an intracellular form ofM
r=60,000 and an extracellular form ofM
r=62,000. All three enzyme forms were glycoproteins with a common polypeptide chain ofM
r=52,000 but with different carbohydrate moieties. No evidence for a high molecular mass precursor form of α-l-fucosidase was found. Fucosidosis is a rare, inherited disease in which α-l-fucosidase activity in tissues and body fluids is low or absent. The mutations for fucosidosis and the serum polymorphism
map separately. Lymphoid cells from two siblings with fucosidosis had 8-fold to 341-fold less intracellular α-l-fucosidase protein with 11-fold to 56-fold lower specific activities than control cells. Residual mutant enzyme was a glycoprotein
with a polypeptide chain virtually the same size (M
r=52,000) as control enzyme. However, residual mutant enzyme was hypoglycosylated and hypersecreted as compared to control
enzyme.
This research was supported by National Institutes of Health Grant DK 32161. 相似文献
19.
Sgambati E Marini M Vichi D Zappoli Thyrion GD Parretti E Mello G Gheri G 《Histochemistry and cell biology》2007,128(3):263-273
The aim of this study was to investigate the distribution of the oligosaccharides of the glycoconjugates in placentas from
pregnancies complicated by different degree of altered glycaemia. Placentas from women with physiological pregnancies (group
1), with pregnancies complicated by minor degree of glucose intolerance (group 2) and with pregnancies complicated by gestational
diabetes mellitus (GDM) treated with insulin (group 3) were collected. Ten lectins were used (ConA, WGA, PNA, SBA, DBA, LTA,
UEA I, GSL II, MAL II and SNA) in combination with chemical and enzymatic treatments. The data showed a decrease of sialic
acid linked α(2–6) to galactose/N-acetyl-d-galactosamine and an increase of N-acetyl-d-glucosamine in the placentas of the pathological groups, in particular the group 3, comparing to the group 1. A decrease
of l-fucose (LTA) and d-galactose-(β1–3)-N-acetyl-d-galactosamine, and an increase and/or appearance of l-fucose (UEA I) and N-acetyl-d-galactosamine were observed in both the pathological groups, particularly in the group 2, with respect to the group 1. In
GDM, and even in pregnancies with a simple alteration of maternal glycaemia, the changes in the distribution of oligosaccharides
could be related to alteration of the structure and functionality of the placenta. 相似文献
20.
Antimicrobial activity of crude seed extract of Moringa oleifera was investigated by thin layer chromatography bioassay against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Cladosporium cladosporioides, and Penicillium sclerotigenum; most of them were prominently inhibited by an isolate with R
F 0.92–0.96. Characterization and identification of the extract revealed the occurrence of three bioactive compounds: 4-(α-l-rhamnopyranosyloxy)benzyl isothiocyanate, methyl N-4-(α-l-rhamnopyranosyloxy) benzyl carbamate (both known compounds), and 4-(β-d-glucopyranosyl-1→4-α-l-rhamnopyranosyloxy)-benzyl thiocarboxamide, existence of which in any Moringa spp. or plant is reported for the first time. The UV spectrum of the novel compound showed maximum absorption at 273 and
225 nm in MeOH while the IR spectrum revealed several characteristic bands at 3100, 2900, 1700, 1500, 1300, 1100 and 1000
cm−1. The 1H-NMR showed signals at 1.2 and 3.77 ppm and the 13C-NMR presented signals at 155, 122, 91.7 and 98.4 ppm. All the compounds at 5 mg/L had very high bactericidal activity against
some of test pathogens even at contact period 1–2 h. 4-(β-d-Glucopyranosyl-1→4-α-l-rhamnopyranosyloxy)benzyl thiocarboxamide was the most potent, with 99.2 % inhibition toward Shigella dysenteriae and 100 % toward Bacillus cereus, E. coli and Salmonella typhi within 4 h of contact. 相似文献