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61.
Ming-Chi Wu Grace K. Arimura John S. Holcenberg Adel A. Yunis 《In vitro cellular & developmental biology. Plant》1982,18(9):750-754
Summary Cultured human pancreatic carcinoma cells (MIA PaCa-2) have been shown previously to be very sensitive toE. coli
l-asparaginase (EC II). The present studies have demonstrated that another enzyme,Acinetobacter glutaminase-asparaginase (AGA) is much more effective in inhibiting cell growth. At the concentration of 0.0025 U/ml of AGA
activity the enzyme totally inhibited cell growth, whereas the EC II with the same concentration did not show any effect.
The inhibition of cell growth correlated well with inhibition of protein and glycoprotein synthesis. The addition ofl-glutamine at the concentration of 1 mM completely reversed the inhibition of protein synthesis. Similarly, the addition ofl-glutamine at the concentration of 3 mM daily on 3 successive days after adding AGA resulted in significant reversal of growth inhibition. The results of this study
indicate that the action of AGA on MIA PaCa-2 is, to a great extent, exerted through itsl-glutaminase activity.
This work was supported in part by USPHS Grant CA 19182. Dr. Wu is recipient of Research Career Development Award Grant CA00686
and Dr. Yunis is a Howard Hughes Investigator. 相似文献
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A method has been developed for quantification of total free and conjugated bile acids separated on silica gel HR coated thin-layer chromatography plates. Aliquots of bile acid solutions are applied to channeled plates which are developed with either ethyl acetate: isooctane: glacial acetic acid 10:10:2 v/v for free bile acid separation, or chloroform:methanol:glacial acetic acid:water 130:50:4:8 v/v for conjugated bile acid separation. Bile acids are determined directly in serial areas of silica gel by treating gel areas suspended in tris buffer with resazurin reagent. The method is quantitative and as little as 0.1 μg of bile acid is readily determined. Application of the method to determinations of bile acids in crude fecal extracts is described. 相似文献
64.
Abstract: Incubation of synaptosomes together with 1-acyl-2-[14 C]arachi-donoyl-sn-glycerophosphoinositols (GPI) and sodium deoxycholate yielded diacylglycerols and free arachidonic acid. Diacylglycerol formation is attributed to hydrolysis by the diacyl-GPI-specific phospholipase C (EC 3.1.4.10), and this reaction requires sodium deoxycholate for optimal activity. The free arachidonic acid formed is attributed to hydrolysis of diacyl-GPI by phospholipase A (EC 3.1.1.5). Free fatty acid release was observed during incubation, even in the absence of bile salts, but this process was preferentially stimulated by sodium taurocholate. The release of fatty acids was not specific for diacyl-GPI, as similar release was obtained during incubation with other phosphoglycerides. In the presence of deoxycholate (2 mg/ml), the release of diacylglycerols was maximal at a diacyl-GPI concentration around 1.0 mM. However, the free fatty acid release was linear with respect to the substrate at least up to 1.4 mM. The rate of diacylglycerol release from diacyl-GPI was more rapid in the initial 30 min, whereas the free fatty acid release was linear with time up to 2 h. Under this incubation condition, calcium was found to stimulate both types of hydrolytic action, although the concentration needed to achieve this stimulation was rather high. This type of labeled precursor is potentially useful for studies of the different modes of diacyl-GPI degradation by enzymes in brain subcellular membranes. 相似文献
65.
James M. Phang Sylvia J. Downing Grace Chao Yeh 《Biochemical and biophysical research communications》1980,93(2):462-470
The reactions catalyzed by proline oxidase and pyrroline-5-carboxylate reductase form a catalytic cycle linking the hexose-monophosphate pentose (HMP) pathway to mitochondrial ATP generation. The cycling of proline and pyrroline-5-carboxylate couples glucose oxidation to ATP generation by a mechanism independent of the Embden-Meyerhof pathway and the tricarboxylic acid cycle. 相似文献
66.
The diol constituent of Rhus cotinus leaf epicuticular wax has been identified as nonacosane-5,10-diol from chemical investigations of the free compound, the TMSi ether and the nonacosane-5,10-dione prepared from the diol by oxidation. The form and distribution of the crystalline waxes changed as the leaves expanded, dense clusters of short tubes covering the thin ribbons formed during the initial stages of growth. The diol content of the wax decreased by more than 50% over the same period. 相似文献
67.
Inhibition of the ATPase by inorganic phosphate, Pi, was examined in terms of product inhibition of the various activities catalyzed by an enzyme preparation from rat brain, and considered in terms of the specific transport processes of the membrane Na+,K+-pump that these activities reflect. The K+-dependent phosphatase activity of the enzyme was most sensitive to Pi, and inhibition was competitive toward the substrate, nitrophenyl phosphate, as would be expected if Pi were released from the same enzyme form that bound substrate. However, this enzymatic activity does not seem to represent a transport process, and thus a cyclical discharge of K+ may not be involved. The Na+-dependent exchange activity was unaffected by Pi, in accord with the absence of Pi release in the reaction sequence. For the corresponding Na+/Na+ exchange function of the pump, which reportedly does not involve ATP hydrolysis either, prior release of Pi obviously cannot be required for Na+ discharge. With the Na+-dependent ATPase activity, measured using micromolar concentrations of ATP, Pi inhibited, but far less than with the phosphatase activity, and inhibition was not competitive toward ATP. Moreover, inhibition decreased as the Na+ concentration was raised from 10 to 100 mM. This elevated concentration of Na+ also led to substrate inhibition. For this ATPase activity, and the corresponding transport process, uncoupled Na+ efflux, the findings suggest that Na+ discharge follows Pi release, in contrast to Na+/Na+ exchange. The ATPase activity, measured with millimolar concentrations of ATP and reflecting the coupled Na+,K+-transport function, was similarly sensitive to Pi, and again inhibition was not competitive toward ATP. However, in this case inhibition did not increase as the Na+ concentration was lowered. For this activity, and the associated transport process, the site of Na+ discharge in the overall reaction sequence remains unresolved. 相似文献
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69.
Abstract— Analysis of whole autopsy brain from a patient with fucosidosis (α-fucosidase deficiency) revealed minor storage of H-antigen glycolipid [Fuc (α, 1→2) Gal-GlcNAc-Gal-Glc-Ceramide] and a slightly abnormal ganglioside composition in the form of a two-fold elevation of GM1 and the presence of a fucose-containing glycolipid (a minor component) which co-migrated with GD1a. The major storage materials in fucosidosis brain were an oligosaccharide (Fuc-Gal-GlcNAc-Man[Fuc-Gal-GlcNAc-Man]-ManGlcNAc) and a disaccharide [Fuc(α, 1→6)-GlcNAc] in the approximate ratio of 5:1. Lesser amounts of a related oligosaccharide (Gal-GlcNAc-Man[Gal-GlcNAc-Man]-Man-GlcNAc) were isolated from the brain of patients with GM1-gangliosidosis (Types I and II) where the major storage material is known to be GM1-ganglioside (Gal (β, 1→3)GalNAc(β, 1→4) [NeuNAcf(α, 2→3) Gal(β, 1→4)Glc-Ceramide). Similarly, a related oligosaccharide (GlcNAc-Man [GlcNAc-Man]-Man-GlcNAc) was isolated from the brain of a patient with a total deficiency of N-acetyl-β-d -hexosaminidase (Sandhoff variant of GM2-gangliosidosis) where the major storage products are known to be GM2-ganglioside (GalNAc (β 1→4) [NeuNAc (α, 2→3)Gal(β, 1→4)Glc-Ceramine) and its asialo derivative. These studies indicate that glycoproteins containing at least 2 mol of l -fucose per oligosaccharide unit are normally catabolized in human brain. Further, it appears that such glycoproteins are initially catabolized by an endo-N-acetylglucosaminidase to release an oligosaccharide which is then degraded by the sequential action of exo-glycosidases. 相似文献
70.