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1.
[目的]为鸟氨酸发酵废液中Ca2＋含量的测定提供参考。[方法]以七氟丁酸为柱中衍生试剂,采用高效液相色谱-蒸发光散射检测器（HPLC-ELSD）法定量测定L-鸟氨酸发酵提取废液中Ca2＋的含量。[结果]在反相C18色谱柱上,以浓度0.14%三氟乙酸（含0.08%七氟丁酸）水溶液-乙腈溶液（84∶16,V∶V）作为流动相,能有效地检测Ca2＋含量,检出限为Ca2＋浓度0.000 2～0.001 6 mol/L。其相应的浓度（Y）与峰面积（X）呈线性关系,线性方程为Y=7×10-10X-3×10-8,相关系数为1.000 0。Ca2＋的平均回收率为99.83%～100.3%,相对标准偏差为0.61%～1.01%。[结论]该方法精密度高,准确度好,稳定性高,能简便、快速、准确地测定鸟氨酸发酵液中Ca2＋的含量。 相似文献
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Triggering of allostery in an enzyme by a point mutation: ornithine transcarbamoylase 总被引：5，自引：0，他引：5
The origin of allostery is an unanswered question in the evolution of complex regulatory proteins. Anabolic ornithine transcarbamoylase, a trimer of identical subunits, is not an allosteric enzyme per se. However, when the active-site residue arginine-106 of the Escherichia coli enzyme is replaced with a glycine through site-directed mutagenesis, the resultant mutant enzyme manifests substrate cooperativity that is absent in the wild-type enzyme. Both homotropic and heterotropic interactions occur in the mutant enzyme. The initial velocity saturation curves of the substrates, carbamoyl phosphate and L-ornithine, conform to the Hill equation. The observed cooperativity depends on substrate but not enzyme concentration. The finding underscores the possibility that a single mutation of the enzyme in the cell could turn transcarbamoylation into a regulatory junction in the biosynthesis of L-arginine and urea. 相似文献
4.
[目的]用微波法合成N^δ-保护鸟氨酸。[方法]以L-鸟氨酸盐酸盐为原料,与碱式碳酸铜反应得到L-鸟氨酸铜络合物,在δ-氨基上分别引入苄氧羰基、叔丁氧羰基、芴甲氧羰基、乙酰基和邻苯二甲酰基,得到了N^δ-保护鸟氨酸铜络合物,微波辐射下用EDTA-2Na脱去铜离子,得到N^δ-苄氧羰基鸟氨酸、Nδ-叔丁氧羰基鸟氨酸、N^δ-芴甲氧羰基鸟氨酸、N^δ-乙酰基鸟氨酸和N^δ-邻苯二甲酰基鸟氨酸5个N^δ-保护鸟氨酸。探讨了微波辐射功率、时间及投料比例对脱铜反应的影响。[结果]脱铜反应的最佳反应条件为：n（N^δ-保护鸟氨酸铜络合物）∶n（EDTA）=1∶1.1～1∶1.2,微波辐射功率为250～300W,反应时间为4～6min,收率分别为93.2%、86.2%、88.7%、86.3%和86.4%（以N^δ-保护鸟氨酸铜络合物计）。产物结构经元素分析和1HNMR确证。[结论]该合成工艺对环境友好、简便、高效,产物收率与纯度均较高。 相似文献
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[目的]用微波法合成Nδ-保护鸟氨酸。[方法]以L-鸟氨酸盐酸盐为原料,与碱式碳酸铜反应得到L-鸟氨酸铜络合物,在δ-氨基上分别引入苄氧羰基、叔丁氧羰基、芴甲氧羰基、乙酰基和邻苯二甲酰基,得到了Nδ-保护鸟氨酸铜络合物,微波辐射下用EDTA-2Na脱去铜离子,得到了Nδ-苄氧羰基鸟氨酸、Nδ-叔丁氧羰基鸟氨酸、Nδ-芴甲氧羰基鸟氨酸、Nδ-乙酰基鸟氨酸和Nδ-邻苯二甲酰基鸟氨酸5个Nδ-保护鸟氨酸。探讨了微波辐射功率、时间及投料比对脱铜反应的影响。[结果]脱铜反应的最佳反应条件为：n（Nδ-保护鸟氨酸铜络合物）∶n（EDTA）=1∶1.1～1∶1.2,微波辐射功率为250～300 W,反应时间为4～6 min,收率分别为93.2%、86.2%、88.7%、86.3%和86.4%（以Nδ-保护鸟氨酸铜络合物计）。产物结构经元素分析和1H NMR确证。[结论]该合成工艺对环境友好、简便、高效,产物收率与纯度均较高。 相似文献
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The enzymatic synthesis of citrulline from ammonia, bicarbonate, adenosine triphosphate, and L-ornithine takes place in the soluble fraction of gut tissue of the earthworm. The synthesis occurs at low ammonia concentrations, is dependent upon added N-acetyl-L-glutamate, and results in incorporation of the bicarbonate carbon into the ureido group of the citrulline molecule. Carbamyl phosphate is the intermediate in the reaction and its biosynthesis in the earthworm is mediated by a carbamyl phosphate synthetase system similar to that of ureotelic vertebrates. 相似文献
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Lesch-Nyhan syndrome: altered kinetic properties of mutant enzyme 总被引：13，自引：0，他引：13
Hypoxanthine-guanine phosphoribosyltransferase is virtually inactive in erythrocytes from patients with the classical Lesch-Nyhan syndrome. In one such patient, activity of this enzyme ranged from 8 to 34 percent of normal in erythrocytes when assayed with a very high concentration of magnesium 5-phosphoribosyl-1-pyrophosphate. In addition, the mutant enzyme exhibited sigmoidal kinetics with this substrate as well as an increased Michaelis constant for both guanine and hypoxanthine. These findings provide the first evidence for genetic heterogeneity within the group of patients with the Lesch-Nyhan syndrome. 相似文献
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An immunoglobulin A of the secretory variety, present in the gastric juice of a patient with pernicious anemia, was shown to have specificity for intrinsic factor. This is the first demonstration in gastric juice of antibody activity restricted to secretory IgA; further, this is the first example of an exocrine (gastric) immune system producing an autoantibody specifically directed toward a product synthesized by that same exocrine organ. 相似文献
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Genetic inactivation of the alpha-galactosidase locus in carriers of Fabry's disease 总被引：11，自引：0，他引：11
Skin fibroblasts from a patient with Fabry's disease showed deficient activity of alpha-galactosidase. Fibroblasts from his mother and sister had two distinct clonal populations, one with enzymatic activity and the other enzyme deficient. This provides evidence of genetic inactivation at the alpha-galactosidase locus and makes possible the detection of carriers of Fabry's disease even when the enzymatic activity in their leukocytes and uncloned fibroblasts is within the range of controls. 相似文献
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After administration of glycine-2-(14)C to a patient with thalassemia, the specific activities of heme and globin of F hemoglobin were consistently higher than those of hemoglobin A. After reaching a maximum, the ratio of the specific activity of heme to that of globin remained constant within each hemoglobin. Explanations considered include dilution by preformed subunits, differential turnover of hemoglobins, and possibly more than one heme-synthesizing pool. 相似文献
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Systemic lupus erythematosus: presence in human serum of an unusual acid-labile leukocyte interferon 总被引：37，自引：0，他引：37
O T Preble R J Black R M Friedman J H Klippel J Vilcek 《Science (New York, N.Y.)》1982,216(4544):429-431
A previously undescribed species of human leukocyte, or alpha, interferon is present in the serum of many patients with systemic lupus erythematosus. It was shown to be alpha-interferon by neutralization with specific antiserums, affinity column chromatography, and antiviral activity on bovine cells. However, 23 of 30 interferon samples tested were inactivated by incubation at pH 2, a characteristic of human "immune," or gamma, interferon. Multiple samples of interferon from the same patient had similar biological properties, but samples from different patients were not all identical, suggesting that several variants of this species of human alpha-interferon may exist. 相似文献
12.
目的 研究急性髓系白血病患者NK细胞CD158受体表位封闭对自身白血病细胞杀伤活性的影响.方法 分离急性髓系白血病患者及健康志愿者外周血NK细胞,以自身白血病细胞及K562细胞为靶细胞,用CCK-8试剂盒检测CD158a、CD158b单克隆抗体封闭前后NK细胞在1：1、5：1、10：1效靶比下对靶细胞的杀伤活性.结果 患者与正常人NK细胞对K562细胞均有高度杀伤活性,且随效靶比增大而增高（P＜0.01）.效靶比为1：1、5：1、10：1时,患者NK胞在封闭前对白血病细胞杀伤活性分别为（1.5±0.3）%、（5.6±0.8）％、（11.8±0.6）%,封闭后分别为（21.8±0.7）％、（38.6±0.9）％、（53.9±1.4）％,各效靶比组封闭前后差异有统计学意义（P＜0.01）.结论 急性髓系白血病患者NK细胞CD158受体表位封闭可提高NK细胞对自身白血病细胞的体外杀伤能力. 相似文献
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Defect in phosphorylation of insulin receptors in cells from an insulin-resistant patient with normal insulin binding 总被引：20，自引：0，他引：20
Mononuclear blood cells were obtained from a patient with type A insulin resistance. The cells showed a normal ability to bind iodine 125-labeled insulin. Analysis of solubilized insulin receptors from the patient's cells revealed a defect in insulin-stimulated tyrosine kinase activity, which is closely associated with the receptor itself. The enzyme failed to phosphorylate the insulin receptor and showed a markedly reduced ability to phosphorylate exogenously added substrates. It appears that receptors from this insulin-resistant patient have a defect distal to the insulin-binding site (the alpha subunit of the receptor). The defect could be located in the beta subunit, which has an adenosine triphosphate-binding site, or in another receptor component that transfers a signal of insulin binding into kinase activity. This dissociation between the normal binding and the defective protein kinase component of the insulin receptor represents the first biochemical defect of the receptor distal to ligand binding. 相似文献
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Purine overproduction in man associated with increased phosphoribosylpyrophosphate synthetase activity 总被引：13，自引：0，他引：13
In hemolyzates from red cells of two brothers with purine overproduction and gout, activity of phosphoribosylpyrophosphate synthetase is more than twofold greater than that measured in normal or other gouty individuals. The increased enzyme activity, which is also demonstrable in fibroblasts of the one patient tested, is associated with increased production of 5-phosphoribosyl-1-pyrophosphate by intact cells, an indication that the enzyme abnormality is the basis for the purine overproduction. This genetic abnormality is an example of an increased enzyme activity producing a disease state. 相似文献
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A technique for the simultaneous audiovisual recording of behavior and brain waves is described. The absence of muscle movement artifact, despite unlimited activity of the patient, suggests that telemetering may be adaptable for routine electroencephalography. 相似文献
16.
Muscle carnitine palmityltransferase deficiency and myoglobinuria 总被引：16，自引：0，他引：16
Muscle carnitine palmityltransferase activity, measured by three different methods, was very low (0 to 20 percent of controls) in a patient with a familial syndrome of recurrent myoglobinuria. Long-chain fatty acyl CoA synthetase activity was normal; acetylcarnitine transferase activity was decreased by 40 percent, and carnitine content was 1.7 times higher than the mean control value. Utilization of palmitate by isolated mitochondria was more impaired than utilization of palmitylcarnitine, suggesting a more severe defect of carnitine palmityltransferase I than transferase II. Thus, myoglobinuria may be due to a genetic defect of lipid metabolism in skeletal muscle. 相似文献
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The origin and mechanisms of human interictal epileptic discharges remain unclear. Here, we describe a spontaneous, rhythmic activity initiated in the subiculum of slices from patients with temporal lobe epilepsy. Synchronous events were similar to interictal discharges of patient electroencephalograms. They were suppressed by antagonists of either glutamatergic or gamma-aminobutyric acid (GABA)-ergic signaling. The network of neurons discharging during population events comprises both subicular interneurons and a subgroup of pyramidal cells. In these pyramidal cells, GABAergic synaptic events reversed at depolarized potentials. Depolarizing GABAergic responses in neurons downstream to the sclerotic CA1 region contribute to human interictal activity. 相似文献
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Ceramidase deficiency in Farber's disease (lipogranulomatosis) 总被引：5，自引：0，他引：5
Ceramidase activity could not be demonstrated in the kidney and cerebellum from a deceased patient with Farber's disease, whereas the activities of six control acid hydrolase enzymes appeared normal. This enzyme defect presumably accounts for the accumulation that has been described in two patients and may represent the biochemical basis of this disorder. 相似文献
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Oxygen-hemoglobulin dissociation curves: effect of inherited enzyme defects of the red cell 总被引：4，自引：0，他引：4
The blood of a patient with a deficiency of hexokinase in the red cells and a decreased concentration of 2, 3-diphosphoglycerate in the red cells showed an increased affinity for oxygen, whereas a patient with a deficiency of pyruvate kinase and an elevated concentration of 2, 3-diphosphoglycerate in the red cells had blood with a decreased affinity for oxygen. Defects in red cell glycolysis may alter the oxygen affinity of blood by virtue of their effect on 2, 3-diphosphoglycerate concentrations in red cells. 相似文献
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Di Ferrante N Ginsberg LC Donnelly PV Di Ferrante DT Caskey CT 《Science (New York, N.Y.)》1978,199(4324):79-81
[1-3H]Galactitol-6-sulfate, N- [1-3H]acetylgalactosaminitol-6-sulfate, N-[1-3H]acetylglucosaminitol-6-sulfate, N-acetylglucosamine-6-sulfate, and 6-sulfated tetrasaccharides from chondroitin-6-sulfate have been used for the measurement of 6-sulfatase activity of extracts of normal skin fibroblasts and of fibroblasts cultured from patients with genetic mucopolysaccharidoses. With these substrates, extracts of fibroblasts derived from Morquio patients lack or have greatly reduced activities for galactitol-6-sulfate, N-acetylgalactosaminitol-6-sulfate, and 6-sulfated tetrasaccharides but have normal activity for N-acetylglucosamine-6-sulfate and its alditol; those derived from a patient with a newly discovered mucopolysaccharidosis have greatly reduced activity for N-acetylglucosamine-6-sulfate and its alditol but normal activity for galactitol-6-sulfate, N-acetylgalactosaminitol-6-sulfate, and the 6-sulfated tetrasaccharides. These findings demonstrate the existence of two different hexosamine-6-sulfate sulfatases, specific for the glucose or galactose configuration of their substrates. Their respective deficiencies, causing inability to degrade keratan sulfate and heparan sulfate in one case and keratan sulfate and chondroitin-6-sulfate in the other, are responsible for different clinical phenotypes. 相似文献