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11.
12.
Claus Braestrup† Mogens Nielsen† Povl Krogsgaard-Larsen‡ 《Journal of neurochemistry》1986,47(3):691-696
[3H]Strychnine binding to rat pons + medulla membranes was used as a measure of glycine receptors or glycine receptor-coupled chloride channels in vitro. A series of compounds structurally related to 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP), which previously were shown to antagonize glycine responses in cat spinal cord, inhibited [3H]strychnine binding in micromolar concentrations. The most potent of these glycine antagonists, 5,6,7,8-tetrahydro-4H-isoxazolo[3,4-d]azepin-3-ol (iso-THAZ), was also the most potent inhibitor of [3H]strychnine binding, with a Ki of 1,400 nM. The Ki value for strychnine was 7.0 nM, whereas the Ki value for the mixed gamma-aminobutyric acid (GABA)/glycine antagonist 3 alpha-hydroxy-16-imino-5 beta-17-aza-androstan-11-one (RU 5135) was only 4.6 nM. Sodium chloride (1,000 mM) enhanced the affinity of strychnine, brucine, isostrychnine, and the nonselective GABA antagonist pitrazepin for [3H]strychnine binding sites, whereas the affinities of glycine, beta-alanine, and taurine were reduced. These sodium chloride shifts, however, were not predictive of antagonist or agonist properties, since the sodium chloride shift for the glycine antagonist iso-THAZ and of the other THIP-related antagonists were similar to those of the glycine-like agonists. The various sodium chloride shifts show that different groups of ligands bind to glycine receptor sites in different ways. 相似文献
13.
Reiner Fischer-Colbrie Claus Hagn Lynn Kilpatrick Hans Winkler 《Journal of neurochemistry》1986,47(1):318-321
We characterized a group of acidic proteins of bovine chromaffin granules with an antiserum raised against a protein described by Rosa and Zanini [Eur. J. Cell Biol. 31, 94-98 (1983)] in pituitary gland. In adrenal medulla the proteins reacting with this antiserum are confined to chromaffin granules. Their largest component has a Mr of 86,000 and a pI of 5.0. In addition six proteins of lower molecular weight are recognized by this antiserum. In a cell-free system only one protein is synthesized that can be precipitated with this antiserum. The properties of these proteins are very similar to those of the previously described chromogranins A and B; however, there is no immunological cross-reaction between these protein groups. We suggest this third group of acidic proteins of chromaffin granules be named chromogranins C. 相似文献
14.
Claus Grunwald 《Phytochemistry》1985,24(12):2915-2918
Six-day-old tobacco seedlings rapidly incorporated and metabolized exogenously supplied [4-14C]-sitosterol, but none of the radioactivity was recovered from stigmasterol. However, exogenously supplied [2-14C]-mevalonic acid was incorporated into both sitosterol and stigmasterol. Based on these results it is suggested that the biosynthetic pathway of stigmasterol is not via sitosterol but that both sterols have a common precursor. 相似文献
15.
Claus König und Helmut Kaiser 《Journal of Ornithology》1985,126(4):443
Summary After a decrease and extinction due to deforestation the population has been reestablished by releasing captive-bred owls. Now about 40 territories are occupied with an average density of 0,8–1,0 territories/10 km2. Highest density: 17 territories/80 km2. 相似文献
16.
The sugar phosphate specificity of rat hepatic 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 总被引:3,自引:0,他引:3
S J Pilkis J Pilkis M R el-Maghrabi T H Claus 《The Journal of biological chemistry》1985,260(12):7551-7556
The sugar phosphate specificity of the active site of 6-phosphofructo-2-kinase and of the inhibitory site of fructose-2,6-bisphosphatase was investigated. The Michaelis constants and relative Vmax values of the sugar phosphates for the 6-phosphofructo-2-kinase were: D-fructose 6-phosphate, Km = 0.035 mM, Vmax = 1; L-sorbose 6-phosphate, Km = 0.175 mM, Vmax = 1.1; D-tagatose 6-phosphate, Km = 15 mM, Vmax = 0.15; and D-psicose 6-phosphate, Km = 7.4 mM, Vmax = 0.42. The enzyme did not catalyze the phosphorylation of 1-O-methyl-D-fructose 6-phosphate, alpha- and beta-methyl-D-fructofuranoside 6-phosphate, 2,5-anhydro-D-mannitol 6-phosphate, D-ribose 5-phosphate, or D-arabinose 5-phosphate. These results indicate that the hydroxyl group at C-3 of the tetrahydrofuran ring must be cis to the beta-anomeric hydroxyl group and that the hydroxyl group at C-4 must be trans. The presence of a hydroxymethyl group at C-2 is required; however, the orientation of the phosphonoxymethyl group at C-5 has little effect on activity. Of all the sugar monophosphates tested, only 2,5-anhydro-D-mannitol 6-phosphate was an effective inhibitor of the kinase with a Ki = 95 microM. The sugar phosphate specificity for the inhibition of the fructose-2,6-bisphosphatase was similar to the substrate specificity for the kinase. The apparent I0.5 values for inhibition were: D-fructose 6-phosphate, 0.01 mM; L-sorbose 6-phosphate, 0.05 mM; D-psicose 6-phosphate, 1 mM; D-tagatose 6-phosphate, greater than 2 mM; 2,5-anhydro-D-mannitol 6-phosphate, 0.5 mM. 1-O-Methyl-D-fructose 6-phosphate, alpha- and beta-methyl-D-fructofuranoside 6-phosphate, and D-arabinose 5-phosphate did not inhibit. Treatment of the enzyme with iodoacetamide decreased sugar phosphate affinity in the kinase reaction but had no effect on the sensitivity of fructose-2,6-bisphosphatase to sugar phosphate inhibition. The results suggest a high degree of homology between two separate sugar phosphate binding sites for the bifunctional enzyme. 相似文献
17.
Ultrastructural localization of the calcium-binding protein parvalbumin in neurons of the song system of the zebra finch,Poephila guttata 总被引:1,自引:0,他引:1
Summary The distribution of parvalbumin (PV) within neurons of the vocal motor nucleus hyperstriatum ventralepars caudalis (HVc) was investigated in the forebrain of adult male zebra finches by means of light and electron microscopy using the indirect immunoperoxidase technique. Parvalbumin-reaction product was located in the amorphous material of perikarya, dendrites and nuclei, and associated to microtubuli, postsynaptic densities and intracellular membranes; it was found in some axons and Gray type-2 boutons, but rarely in type-1 boutons and never in the Golgi apparatus. These observations suggest that parvalbumin may regulate calcium-dependent processes at the postsynaptic membrane and in the cytosol. Furthermore, the partial association of parvalbumin to microtubuli points to an involvement in calcium-dependent tubular functions. Calcium currents and microtubular assembly or transport may be relevant for the known functions of HVc in song learning. 相似文献
18.
Summary Isopenicillin N epimerase activity in Cephalosporium acremonium CW-19 is so labile that it has never been detected in sonic extracts. Prior to this work, it had only been obtained by the laborious protoplast lysate procedure. The present work shows that the enzyme is present in sonic extracts of a high cephalosporin-producing strain (C-10) of C. acremonium throughout the fermentation. 相似文献
19.
Isocitrate Dehydrogenase and Glutamate Synthesis in Acetobacter suboxydans 总被引:5,自引:4,他引:1 下载免费PDF全文
Acetobacter suboxydans is an obligate aerobe for which an operative tricarboxylic acid cycle has not been demonstrated. Glutamate synthesis has been reported to occur by mechanisms other than those utilizing isocitrate dehydrogenase, a tricarboxylic acid cycle enzyme not previously detected in this organism. We have recovered alpha-ketoglutarate and glutamate from a system containing citrate, nicotinamide adenine dinucleotide (NAD), a divalent cation, pyridoxal phosphate, an amino donor, and dialyzed, cell-free extract. Aconitase activity was readily detected in these extracts, but isocitrate dehydrogenase activity, measured by NAD reduction, was masked by a cyanide-resistant, particulate, reduced NAD oxidase. Isocitrate dehydrogenase activity could be demonstrated after centrifuging the extracts at 150,000 x g for 3 hr and treating the supernatant fluid with 2-heptyl-4-hydroxyquinoline N-oxide. It is concluded that A. suboxydans can utilize the conventional tricarboxylic acid cycle enzymes to convert citrate to alpha-ketoglutarate which can then undergo a transamination to glutamate. 相似文献
20.
Summary From studies of the DNA base composition of Microcyclus species, it is concluded that the genus is to be regarded as a taxonomically heterogeneous group. This agrees with morphological observations of the different species. 相似文献