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排序方式: 共有118条查询结果,搜索用时 15 毫秒
1.
Solov'eva ON Meshalkina LE Kovina MV Selivanov VA Bykova IA Kochetov GA 《Biochemistry. Biokhimii?a》2000,65(10):1202-1205
Two substrates of the transketolase reaction are known to bind with the enzyme according to a ping-pong mechanism [1]. It is shown in this work that high concentrations of ribose-5-phosphate (acceptor substrate) compete with xylulose-5-phosphate (donor substrate), suppressing the transketolase activity (Ki = 3.8 mM). However, interacting with the donor-substrate binding site on the protein molecule, the acceptor substrate, unlike the donor substrate, does not cause any change in the active site of the enzyme. The data are interesting in terms of studying the regulatory mechanism of the transketolase activity and the structure of the enzyme-substrate complex. 相似文献
2.
Shavva AG Morozkina SN Ishchenko IV Eliseev II Selivanov SI Abusalimov ShN Selivanov SS Kameneva IIu Eshchenko ND 《Bioorganicheskaia khimiia》2007,33(3):310-314
Modifications of 6-oxa-D-homo-8alpha-analogues of steroid estrogens were found to lead to a complete loss of the uterotropic and hypertriglyceridemic activities. These compounds may be promising for the design on their basis of inhibitors of the steroid hormone metabolism and transporters of other compounds to the estrogen target organs. 相似文献
3.
All the signals in the 1H and 13C NMR spectra of some analogues of 7alpha-methyl-8alpha- and 6-oxa-8alpha-steroid estrogens were completely assigned. Considering the values of nuclear Overhauser effect and vicinal coupling constants, these steroids were shown to exhibit a fast, on the NMR time scale, conformational equilibrium arising due to the inversion of ring B. The conformer populations were obtained from a comparison of the experimental and theoretical values of the dihedral angles and the interproton distances. This conformational equilibrium was shown to depend on the nature of atom in position 6: for the 7alpha-methyl-6-oxa-8alpha analogues of the steroid estrogens, the population of the conformer with the pseudoaxial orientation of the 7alpha-methyl group was observed to be decreased compared with the 7alpha-methyl-8alpha analogue. 相似文献
4.
S. I. Selivanov A. Yu. Solov’ev S. N. Morozkina A. G. Shavva 《Russian Journal of Bioorganic Chemistry》2007,33(3):302-309
All the signals in the 1H and 13C NMR spectra of some analogues of 7α-methyl-8α-and 6-oxa-8α-steroid estrogens were completely assigned. Considering the values of nuclear Overhauser effect and vicinal coupling constants, these steroids were shown to exhibit a fast, on the NMR time scale, conformational equilibrium arising due to the inversion of ring B. The conformer populations were obtained from a comparison of the experimental and theoretical values of the dihedral angles and the interproton distances. This conformational equilibrium was shown to depend on the nature of atom in position 6: for the 7α-methyl-6-oxa-8α analogues of the steroid estrogens, the population of the conformer with the pseudoaxial orientation of the 7α-methyl group was observed to be decreased compared with the 7α-methyl-8α analogue. 相似文献
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Solovjeva ON Sevostyanova IA Yurshev VA Selivanov VA Kochetov GA 《The protein journal》2012,31(2):137-140
Catalytic activity has been demonstrated for holotransketolase in the absence of free bivalent cations in the medium. The
two active centers of the enzyme are equivalent in both the catalytic activity and the affinity for the substrates. In the
presence of free Ca2+ (added to the medium from an external source), this equivalence is lost: negative cooperativity is induced on binding of
either xylulose 5-phosphate (donor substrate) or ribose 5-phosphate (acceptor substrate), whereupon the catalytic conversion
of the bound substrates causes the interaction between the centers to become positively cooperative. Moreover, the enzyme
total activity increase is observed. 相似文献
7.
Vitaly A. Selivanov Marta Cascante Mark Friedman Mark F. Schumaker Massimo Trucco Tatyana V. Votyakova 《PLoS computational biology》2012,8(9)
The mitochondrial electron transport chain transforms energy satisfying cellular demand and generates reactive oxygen species (ROS) that act as metabolic signals or destructive factors. Therefore, knowledge of the possible modes and bifurcations of electron transport that affect ROS signaling provides insight into the interrelationship of mitochondrial respiration with cellular metabolism. Here, a bifurcation analysis of a sequence of the electron transport chain models of increasing complexity was used to analyze the contribution of individual components to the modes of respiratory chain behavior. Our algorithm constructed models as large systems of ordinary differential equations describing the time evolution of the distribution of redox states of the respiratory complexes. The most complete model of the respiratory chain and linked metabolic reactions predicted that condensed mitochondria produce more ROS at low succinate concentration and less ROS at high succinate levels than swelled mitochondria. This prediction was validated by measuring ROS production under various swelling conditions. A numerical bifurcation analysis revealed qualitatively different types of multistationary behavior and sustained oscillations in the parameter space near a region that was previously found to describe the behavior of isolated mitochondria. The oscillations in transmembrane potential and ROS generation, observed in living cells were reproduced in the model that includes interaction of respiratory complexes with the reactions of TCA cycle. Whereas multistationarity is an internal characteristic of the respiratory chain, the functional link of respiration with central metabolism creates oscillations, which can be understood as a means of auto-regulation of cell metabolism. 相似文献
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A study was made of the kinetics of thrombocytopoiesis restoration in lethally irradiated mice after transplantation to them of the donor marrow cells. In the initial period, the thrombocytopoiesis restoration is provided by transite cells-precursors of megakaryocytes present in the transplanted bone marrow; the subsequent restoration is due to cells of the self-maintaining population. The level of restoration does not correlate with the number of polypotent cells that form macrocolonies in the spleen of irradiated recipients. 相似文献