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1.
The GSH dependence of the metabolic pathways involved in the conversion of cysteine to sulfate in intact cells has been investigated. It was found that hepatocyte-catalysed sulfate formation from added
-cysteine did not occur if hepatocyte GSH was depleted beforehand, but was restored when GSH levels recovered. Furthermore, sulfate formation did not recover in GSH-depleted hepatocytes if GSH synthesis was prevented with buthionine sulfoximine. Thiosulfate formation was, however, markedly enhanced in GSH-depleted hepatocytes. These results suggest that thiosulfate is an intermediate in the formation of inorganic sulfate from
-cysteine and that GSH was required for the conversion of thiosulfate to inorganic sulfate. Much less sulfate was formed if the cysteine was replaced with cysteinesulfinate. Furthermore, sulfate formation from
-cysteine was markedly inhibited by the addition of the transaminase inhibitor
-cycloserine or the γ-cystathionase inhibitor
-propargylglycine. The major routes of sulfate formation from
-cysteine therefore seems to involve pathways that do not involve
-cysteinesulfinate. Similar amounts of sulfate were formed from
-cysteine as
-cysteine. Thiosulfate instead of sulfate was also formed in GSH-depleted hepatocytes. However, sulfate formation from
-cysteine differed from
-cysteine in that it was inhibited by the
-aminoacid oxidase inhibitor sodium benzoate and was not affected by transaminase or γ-cystathionase inhibitors. These results suggest that thiosulfate is an intermediate in sulfate formation from
-cysteine and involves the oxidation of
-cysteine by
-amino acid oxidase to form β-mercaptopyruvate. 相似文献
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2.
Synthesis of methyl
-Ribose was converted into methyl
and this, on tin-mediated allylation, gave a mixture of the 2-O-allyl and 3-O-allyl derivatives which were separated by chromatography. The more polar isomer was characterised as the 3-O-allyl derivative after conversion via
(which was also synthesised from
) into the known
. Methyl
was converted into methyl
via methyl
. 相似文献
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3.
Takashi Arima Yoshihisa Kitamura Tadashi Nishiya Takashi Taniguchi Hiroshi Takagi Yasuyuki Nomura 《Neurochemistry international》1997,30(6):964
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4.
Mutacins are bactericidal substances of proteinaceous nature produced by Streptococcus mutans. Lantibiotics are antibacterial substances containing post-translationally modified amino acids such as lanthionine. Mutacin B-Ny266 was purified from the cell pellet of S. mutans strain Ny266 by ethanol extraction at pH 2.0 followed by reversed-phase chromatography (Sep-Pak® cartridge) and by HPLC on a C18 column. The mean purification factor was 3240±81 and the mean yield was 1.0±0.1%. Molecular mass of mutacin B-Ny266 as determined by mass spectroscopy is 2270.29±0.21 Da. The amino acid sequence of the purified active fraction was obtained by Edman degradation after treatment with alkaline ethanethiol. Twenty-one amino acids were detected in this analysis. Mutacin B-Ny266 belongs to the type A lantibiotics. The proposed sequence is: F–K–
–W–U–F–
–
–P–G–
–A–K–O–G–
–F–N–
–Y–
. The molecule differs from that of epidermin/staphylococcin 1580 and gallidermin at positions 1, 2, 4, 5 and 6. 相似文献
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5.
Katsumi Ajisaka Ichiro Matsuo Megumi Isomura Hiroshi Fujimoto Mayumi Shirakabe Mitsuyo Okawa 《Carbohydrate research》1995,270(2)
Various manno-oligosaccharides including
and
were formed when a highly concentrated mannose solution was incubated in the presence of α-mannosidase from Aspergillus niger.
and
were isolated by activated carbon chromatography followed by high performance liquid chromatography using an amino-silica column. In addition to the above oligosaccharides,
, and
were also isolated. 相似文献
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6.
The dissociation constant (Kd) for CO from neuronal nitric oxide synthase heme in the absence of the substrate and cofactor was less than 10−3 μM. In the presence of
-Arg, it dramatically increased up to 1 μM. In the presence of inhibitors such as NG-nitro-
-arginine methyl ester and 7-nitroindazole (NI), the Kd value further increased up to more than 100 μM. Addition of the cofactor, 5,6,7,8-tetrahydrobiopterin (H4B), increased the Kd value by 10-fold in the presence of
-Arg, whereas it decreased the value to less than one 250th in the presence of NI. Addition of H4B increased the recombination rate constant (kon) for CO by more than two-fold in the presence of
-Arg or N6-(1-iminoethyl)-
-lysine, whereas it decreased the kon value by three-fold in the presence of
-thiocitrulline. Thus, the binding fashion of some of inhibitors, such as NI, may be different from that of
-Arg with respect to the H4B effect. 相似文献
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7.
Substrate specificity of purified acetylxylan esterase (AcXE) from Trichoderma reesei was investigated on partially and fully acetylated methyl glycopyranosides. Methyl 2,3,4-tri-O-acetyl-β-
-xylopyranoside was deacetylated at positions 2 and 3, yielding methyl 4-O-acetyl-β-
-xylopyranoside in almost 90% yield. Methyl 2,3-di-O-acetyl β-
-xylopyranoside was deacetylated at a rate similar to the fully acetylated derivative. The other two diacetates (2,4- and 3,4-), which have a free hydroxyl group at either position 3 or 2, were deacetylated one order of magnitude more rapidly. Thus the second acetyl group is rapidly released from position 3 or 2 after the first acetyl group is removed from position 2 or 3. The results strongly imply that in degradation of partially acetylated β-1,4-linked xylans, the enzyme deacetylates monoacetylated xylopyranosyl residues more readily than di-O-acetylated residues. The T. reesei AcXE attacked acetylated methyl β-
-glucopyranosides and β-
-mannopyranosides in a manner similar to the xylopyranosides. 相似文献
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8.
Molecular cloning and characterization of FHL2, a novel LIM domain protein preferentially expressed in human heart 总被引:14,自引:0,他引:14
Kwok Keung Chan Stephen Kwok Wing Tsui Simon Ming Yuen Lee Sharon Chui Wah Luk Choong Chin Liew Kwok Pui Fung Mary Miu Yee Waye Cheuk Yu Lee 《Gene》1998,210(2):41-350
A full-length cDNA clone encoding a novel LIM-only protein was isolated and sequenced from a human fetal heart cDNA library. This full-length clone consists of 1416 base pairs and has a predicted open reading frame (ORF) encoding 279 amino acids. The ORF of this polypeptide codes for the human heart-specific
our and a
alf
IM-only protein
(FHL2). It possesses an extra zinc finger that is a half LIM domain and four repeats of LIM domain. When the human FHL2 cDNA probe was used to hybridize with poly-A RNA of various human tissues, a very strong signal could be seen in heart tissues, and only moderately low signals could be detected in placenta, skeletal muscle and ovary. Virtually no signal could be detected in brain, lung, liver, kidney, pancreas, spleen, thymus, prostate, testis, small intestine, colon or peripheral blood leukocyte. FHL2 was mapped to chromosome 2q12–q13 by fluorescent in-situ hybridization (FISH). 相似文献
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9.
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10.
Daniela Alberati-Giani Andrea M. Cesura Clemens Broger William D. Warren Stephan Rver Pari Malherbe 《FEBS letters》1997,410(2-3)
Kynurenine 3-monooxygenase, an NADPH-dependent flavin monooxygenase, catalyses the hydroxylation of
-kynurenine to
-3-hydroxykynurenine. By hybridization screening using a cDNA probe encoding the entire exon 2 of Drosophila melanogaster kynurenine 3-monooxygenase, we isolated a 2.0 kb cDNA clone coding for the corresponding human liver enzyme. The deduced amino acid sequence of the human protein consists of 486 amino acids with a predicted molecular mass of 55 762 Da. Transfection of the human cDNA in HEK-293 cells resulted in the functional expression of the enzyme with kinetic properties similar to those found for the native human protein. RNA blot analysis of human tissues revealed the presence of a major mRNA species of 2.0 kb in liver, placenta and kidney. 相似文献
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11.
Luciano Lepri Massimo Del Bubba Rita Maggini Gian Paolo Donzelli Paola Galvan 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,704(1-2)
Pooled human milk was subjected to Holder pasteurization and storage at −20°C up to 90 days and examined for its content of fat and
-lactate and for lipid composition. This treatment reduced fats by 6% and
-lactate by at least 7%. In addition, pasteurization and storage induced triglyceride hydrolysis. The absolute amount of free fatty acids (FFAs) which was 0.5% after collection, doubled after pasteurization and rose even more after storage. Different FFA compositions were found by several authors using the same analytical method even for milk samples subjected to the same treatment. More detailed information on procedures must be given to explain the different results. 相似文献
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12.
The catalytic reduction of
-glyceraldehyde to glycerol by aldose reductase has been investigated with the combined potentials of quantum mechanics (QM) and molecular mechanics (MM) to resolve the question of whether Tyr48 or His110 serves as the proton donor during catalysis. Site directed mutagenesis studies favor Tyr48 as the proton donor while the presence of a water channel linking the Nδ1 of His110 to the bulk solvent suggests that His110 is the proton donor. Utilizing the combined potentials of QM and MM, the binding mode of substrate
-glyceraldehyde was investigated by optimizing the local geometry of Asp43, Lys77, Tyr48, His110 and NADPH at the active site of aldose reductase. Reaction pathways for the reduction of
-glyceraldehyde to glycerol were then constructed by treating both Tyr48 and His110 as proton donors. Comparison of energetics obtained from the reaction pathways suggests His110 to be the proton donor. Based on these findings, a reduction mechanism of
-glyceraldehyde to glycerol is described. 相似文献
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13.
Toshiyuki Chikuma Misaki Kishii Kyoji Taguchi Ryuichi Yajima Takeshi Kato Y. Peng Loh Yoko Ishii Akira Tanaka 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,703(1-2)
A rapid and sensitive assay method for the determination of glycine carboxypeptidase activity has been reported. This method is based on the monitoring of the absorption at 460 nm of 4-dimethylaminoazobenzene-4′-sulfonyl-Gly-
-Phe, enzymatically formed from the substrate 4-dimethylaminoazobenzene-4′-sulfonyl-Gly-
-Phe-Gly, after separation by high-performance liquid chromatography (HPLC) using a TSK gel ODS-80TM reversed-phase column by isocratic elution. This method is sensitive enough to measure 4-dimethylaminoazobenzene-4′-sulfonyl-Gly-
-Phe at concentrations as low as 1 pmol and yield highly reproducible results and requires less than 7.5 min per sample for separation and quantitation. The pH optimum for glycine carboxypeptidase activity was 4.8 to 5.4. The Km and Vmax values were respectively 21.1 μmol and 3.73 pmol/μg/h with the use of enzyme extract obtained from bovine pituitary. Glycine carboxypeptidase activity was strongly inhibited by Ag+, Cu2+ and p-chloromercuriphenylsulfonic acid. Among the organs examined in a mouse, the highest specific activity of the enzyme was found in testis. The sensitivity and selectivity of this method will aid in efforts to examine the physiological role of this peptidase. 相似文献
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14.
Luciano Maestri Sergio Ghittori Marcello Imbriani 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1996,687(2):1334
A method for the determination of urinary
(M1) and
(M2) in man was developed. Clean-up of urine samples was obtained by a chromatographic technique using a short reversed-phase precolumn; purified samples were then deacetylated with porcine acylase I for 16 h at 37°C and deproteinized by centrifugal ultrafiltration. Derivatization was performed with o-phthaldialdehyde and 2-mercaptoethanol and the fluorescent derivatives were separated on a reversed-phase analytical column with a gradient mobile phase consisting of 50 mM acetate buffer (pH 6.5) and methanol. The retention times of the diastereoisomers of M1 (M1-“S” and M1-“R”) were 52.8 and 73.7 min, respectively; M2 diastereoisomers eluted as a single peak at 70.5 min. The fluorescence detector was set at 330 nm (excitation) and 440 nm (emission). The detection limit (at a signal-to-noise ratio of three) was about 7 μg/l. The method was applied to 25 urine samples from workers exposed to styrene. A relationship was found between urinary mandelic and phenylglyoxylic acids and mercapturic acids specific for styrene. Urine samples from ten non-exposed subjects showed no detectable amounts of analytes. 相似文献
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15.
Process for the isolation of preparative quantities of
Paul A. Kroon Maria T. Garcia Conesa Ian J. Colquhoun Gary Williamson 《Carbohydrate research》1997,300(4)
Specific enzymes were used to hydrolyse sugarbeet pulp to facilitate the isolation of
in preparative amounts. The feruloylated arabinose disaccharide was purified by chromatography on Sephadex LH-20 and Bio-Gel P-2 and the structure confirmed by NMR and UV spectroscopy and high-performance liquid chromatography. 相似文献
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16.
R. Bhushan G. Thuku Thiongo 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1998,708(1-2)
The resolution of (±)-atenolol, (±)-propranolol and (±)-metoprolol into their enantiomers was achieved by TLC on silica-gel plates impregnated with optically pure
-lysine (0.5%) and
-arginine (0.5%) as the chiral selectors. In all cases, different combinations of acetonitrile–methanol solvent systems were found to be successful in resolving these compounds. Spots were detected using iodine vapour. The detection limit for both (±)-atenolol and (±)-propranolol was 2.6 μg and for (±)-metoprolol, it was 0.26 μg. 相似文献
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17.
Mass spectrometric quantification of the mu opioid receptor agonist Tyr-
Olga O. Grigoriants Jih-Lie Tseng Robert R. Becklin Dominic M. Desiderio 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,695(2)
The mu opioid receptor agonist Tyr-
-Arg-Phe-Lys-Amide (
-Arg2-Lys4-Dermorphin1-4amide=DALDA) was infused continuously for 2 h into sheep. The presence of DALDA in ovine plasma was determined by reversed-phase high-performance liquid chromatography (RP-HPLC) and mass spectrometry (MS) in plasma samples that were obtained at different times during and following that infusion. A stable isotope-incorporated internal standard, deuterated DALDA (d5-DALDA), was used for the MS quantification of DALDA via the protonated molecule ion, (M+H)+, of DALDA and of d5-DALDA. Time-course data (μg DALDA ml−1 plasma vs. time) were obtained. Tandem MS (MS–MS) provided the product-ion spectrum of the (M+H)+ ion of DALDA in one of the samples to confirm the amino acid sequence of DALDA. 相似文献
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18.
Reaction of FcCCo3(CO)9 with 2,3-bis(diphenylphosphino)maleic anhydride (bma). X-ray diffraction structure and redox properties of
The reaction between the tricobalt cluster FcCCo3(CO)9 (1) (where Fc = ferrocenyl) and the redox-active diphosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) affords the new cluster
(3) in refluxing 1,2-dichloroethane or toluene. The cluster FcCCo3(CO)7(bma) (2), a logical precursor to 3, was observed in solution by IR spectroscopy when cluster 1 and bma were refluxed in the low boiling point solvent CH2Cl2; however, putative 2 could not be isolated due to its rapid conversion to the final product 3. Cluster 3 has been fully characterized in solution by IR and NMR (13C and 31P) spectroscopy and in the solid state by X-ray diffraction analysis.
, as the CH2Cl2 solvate, crystallized in the triclinic space group
for 3602 observed reflections with 13σ(I). Cyclic voltammetric investigations of 3 in CH2Cl2 reveal the presence of three reversible redox responses assigned to the 0/1+, 0/1−1, and 1−/2− redox couples. The nature of the HOMO and the two lowest unoccupied molecular orbitals (LUMO and SUMO) in 3 has been determined by carrying out extended Hückel calculations on the model compound
, the results of which are discussed relative to the observed electrochemistry of 3 and related cluster compounds. 相似文献
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19.
The title oligosaccharides, the tri-through the hexasaccharide in the Inaba series and the penta- and the hexasaccharide in the Ogawa series, have been synthesized using 1-thioglycosides of precursors to 3-O-benzyl-perosamine (4-amino-4,6-dideoxy-
-mannose) as building blocks and N-iodosuccinimide/silver triflate as a promoter. The azido groups in the assembled oligosaccharides were reduced to amino groups, which were then acylated using
acid as the derivatizing reagent. Catalytic hydrogenolysis, simultaneously of the benzyl and benzylidene groups, gave the desired products that were characterized by 1H and 13C NMR spectroscopy. 相似文献
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20.
A general and flexible synthetic approach to biologically important 5,6-unsaturated C18-phytosphingosines was developed via olefin cross-metathesis employing truncated C6-phytosphingosines as the key intermediates. These were efficiently prepared in high yields by zinc-mediated reductive opening of methyl 2-amino-2-deoxy-β-hexopyranosides.
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