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991.
K Murakami 《Journal of biochemistry》1979,86(5):1331-1336
The kinetic and molecular properties of AMP deaminase [AMP aminohydrolase, EC 3.5.4.6] purified from baker's yeast (saccharomyces cerevisiae) were investigated. The enzyme was activated by ATP and dATP, but inhibited by Pi and GTP in an allosteric manner. Alkali metal ions and alkaline earth metal ions activated the enzyme to various extent. Kinetic negative cooperativity was observed in the binding of nucleoside triphosphates. Kinetic analysis showed that the number of interaction sites for AMP (substrate) and Pi (inhibitor) is two each per enzyme molecule. The molecular weight of the native enzyme was estimated to be 360,000 by sedimentation equilibrium studies. On polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, the enzyme gave a single polypeptide band with a molecular weight of 83,000, suggesting that the native enzyme has a tetrameric structure. Baker's yeast AMP deaminase was concluded to consist of two "promoter" units which each consist of two polypeptide chains with identical molecular weight. 相似文献
992.
The serum estradiol concentration and bone mineral content of the right radius were determined in 34 postmenopausal females. Regression analysis showed a significant positive correlation between the serum estradiol concentration and bone mineral content of the right radius (r=0.477, p less than 0.01). These results support the view that the decreased level of serum estrogens is one of the major factors involved in the loss of bone mass with age. 相似文献
993.
The flow measurement of each component in each compartment is important in works on transport phenomena in a biological system. The method of flow measurement was studied adopting the capacitor concept derived from network thermodynamics.A biologically active component i in a compartment is defined as follows, where the total quantity ni consists of a measurable form ni (free form, conc. c1) and concealed form n2 (conc, c2). Capacitor for the species i of a compartment is defined as follows, , Thus flow of each component is expressed as, , Method of determination of capacitor coefficients A and B by titration experiment was also considered. For an experimental case, the capacitance for H+ of blood compartment was determined. The relationship between the capacitor concept and the buffer value of Van Slyke was discussed. 相似文献
994.
The radioprotective agent cysteamine can prevent the teratogenic action of 5-azacytidine in rat fetuses. The preventive influence of cysteamine was observed when applied to the mother not only 3 hours and 30 minutes before the 5-azacytidine administration, but also 30 minutes after it. However, the application of cysteamine 3 hours after the administration of 5-azacytidine showed no preventive influence. 相似文献
995.
Possible mutagenic activity of captan was investigated by in vitro and in vivo cytogenetic studies and by the dominant lethal study in mice. In vitro cytogenetic study with cultured human diploid cells revealed a significant increase in the frequency of cells showing stickiness and a severe mitotic inhibition at concentrations of 3.0 and 4.0 microgram of captan per ml. although no chromosomal aberrations were observed. In in vivo cytogenetic study, no chromosomal aberrations were induced in the bone marrow cells of rats treated orally with captan at a single dose of 500, 1000 or 2000 mg/kg or at five consecutive doses of 200, 400 or 800 mg/kg/day. Dominant lethal study also failed to show any mutation induction after treatment of male mice with daily oral dose of 200 or 600 mg of captan per kg bw for five days. 相似文献
996.
Akira Murakami Hachiro Inokuchi Haruo Ozeki Hideo Yamagishi 《Molecular & general genetics : MGG》1977,155(2):139-143
Summary During vegetative growth, the su+3-transducing phage of 80 segregates progeny phage which has lost the su+3-transducing fragment. Average burst size of the transducing phage is less than one tenth that of the segregant. Burst size of the transducing phage was recovered to the normal level when segregant-type phage was co-infected as a helper. We suspected that the maturation process was partially inhibited by a polar effect caused by insertion of the su+3-transducing fragment into the continuity of 80 late genes. To determine which gene expressions are partially inhibited in the transducing phage, various amber mutants were used as the helper phage and burst size of the transduzing phage was measured in the system where excision of the transducing fragment was inhibited. The results indicated that gene expression of a group of genes 4 to 13 was reduced in the transducing phage, while that of a group of genes 1, 2 and 3 was not. The specificity of partial inhibition of gene function agrees well with the results of physical mapping of the transducing fragment; that is, the fragment was inserted within the region of gene 4 by heteroduplex analysis (Yamagishi et al., 1976a). 相似文献
997.
Mating factor is a peptide excreted into the culture fluid by alpha-mating type cells of Saccharomyces cerevisiae X-2180 1B. The purification of the mating factor was carried out by ion exchange chromatography on phosphocellulose and Amberlite IRC 50 columns, followed by gel filtration on a Sephadex LH 20 column. The factor thus prepared was a peptide composed of Lys1, His1, Trp2, Gln2, Pro2, Gly1, Met1, Leu2 and Tyr1, and was able to induce morphological changes on alpha-mating type cells at a concentration of 5 pg/ml. The amino acid sequence of the mating factor was determined by the manual Edman degradation method using intact mating factor and its thermolytic peptides. The C-terminal amino acid residue was determined by digesting the factor with carboxypeptidase A. The complete amino acid sequence of the mating factor was established to be as follows: Trp-His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr. 相似文献
998.
999.
New fluorogenic substrates for renin 总被引:1,自引:0,他引:1
Kazuo Murakami Tamiko Ohsawa Shigehisa Hirose Katsumi Takada Shumpei Sakakibara 《Analytical biochemistry》1981,110(1):232-239
A simple and sensitive fluorometric assay was developed to test renin activity within several hours. Two new fluorogenic peptides, Arg-Pro-Phe-His-Leu-Leu-Val-Tyr-4-methylcoumaryl-7-amide (octapeptide-MCA) and a succinyl derivative of the octapeptide-MCA were synthesized and used as a renin substrate. Renin cleaved the substrates at the Leu-Leu bond, releasing Leu-Val-Tyr-MCA. Three amino acids of this product were then successively split off by the auxiliary enzyme, leucine aminopeptidase, to liberate free 7-amino-4-methylcoumarin (AMC). The generation of the fluorescent 7-amino-4-methylcoumarin was proportional to renin concentrations up to 100 mGoldblatt U/tube. The optimal pH of renin reaction for both substrates was 6.5 to 7.0. As low as 5 mGoldblatt U of renin could be detected by this method. This method was applied to the assay of renin during its purification. 相似文献
1000.
ATP and pyrophosphate at high concentration (greater than 1 mM) inhibited photophosphorylation of isolated spinach chloroplasts in the normal salt medium and did not cause stimulation of electron transport. The inhibition of photophosphorylation by ATP or pyrophosphate was shown to be abolished by the addition of excess MgCl2, ADP and phosphate. It has been demonstrated that the rates of photophosphorylation in the absence and presence of ATP or pyrophosphate are determined similarly by the concentrations of magnesium-ADP (Mg - ADP-) and magnesiumphosphate (Mg - Pi) complexes. It is highly probable that Mg - ADP- and Mg - Pi, but not free ADP and free phosphate, are the active form of the substrates of photophosphorylation. This is in support of the view that ATP inhibits photophosphorylation by decreasing the concentration of Mg2+ which is available for the formation of the complex with ADP and phosphate. 相似文献