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Kinetic and regulatory properties of NADP-isocitrate dehydrogenase (NADP-IDH) and aspartate aminotransferase (AsAT) responsible for 2-oxoglutarate metabolism in the cytoplasm and mitochondria of rat liver were studied. Based on the subcellular location of these enzymes and their kinetic parameters (Km, Ksi) obtained with highly purified enzyme preparations, it is suggested that synthesis of 2-oxoglutarate should be mainly determined by cytoplasmic NADP-IDH (86% of the total activity in the cell), whereas its utilization should depend on cytoplasmic AsAT (78% of the total activity). AsAT from the rat liver was specified by substrate inhibition and also by changes in the enzyme affinity for the substrates under the influence of some intermediates of the tricarboxylic acid cycle: isocitrate, succinate, fumarate, and citrate. Key intermediates of nitrogen metabolism (glutamate, glutamine, and aspartate) are involved in the regulation of NADP-IDH and AsAT. These enzymes are regulated oppositely, and the catalytic activity of one enzyme can be stimulated concurrently with a decrease in the activity of the other. Obviously, carbon and nitrogen metabolism in the rat liver can be controlled through redistribution of 2-oxoglutarate between different metabolic processes via regulatory mechanisms influencing differently located forms of NADP-IDH and AsAT. 相似文献
114.
Popova AV Zhilenkov EL Myakinina VP Krasilnikova VM Volozhantsev NV 《FEMS microbiology letters》2012,326(1):40-46
Wallemia sebi is a xerotolerant, ubiquitous, food-borne, mycotoxigenic fungus. An ethanol extract of its mycelium demonstrated a strong hemolytic activity, which was further enhanced at high salt concentrations in the growth medium. Characterization of the extract using gas chromatography-mass spectrometry revealed a mixture of sterols and unsaturated fatty acids, indicating the latter as responsible for the hemolytic activity. The lytic activity of the extract is here studied using red blood cells and artificial small lipid vesicles with various lipid compositions. This shows concentration-dependent hemolysis and preferential activity toward lipid membranes with greater fluidity. The W.?sebi lytic activity on mammalian erythrocytes shows its potential involvement in the formation of lesions in subcutaneous infections, in farmer's lung disease, and in consumption of food and feed that are contaminated with food-borne W.?sebi. 相似文献
115.
Studying plant root kinematics is important for understanding certain aspects of root growth and movement, which are strictly
correlated in plants. However, there is little available data on autonomous movements in plant roots, such as nutations, and
the data that are available are poorly described. We investigated the autonomous movements during growth in primary maize
roots by estimating the main kinematic parameters of nutations (i.e., the period of duration and amplitude) and the growth
rate. The estimations of nutation parameters were performed by developing dedicated methods, which are based on the analysis
of root tip displacement and tip velocity. The data relative to the tip displacements were obtained using tip tracing software
developed by our team specifically for this purpose. The results confirmed that the nutational phenomenon covers the continuous
range of periods and amplitudes, with certain dominant period-amplitude types, which we clustered into three groups: i) amplitudes
less than 0.1 mm and 4–16 min periods, ii) amplitudes less than 0.1 mm and 20–120 min periods, and iii) amplitudes greater
than 0.1 mm and 24–120 min periods. 相似文献
116.
Influence of drying on the secondary structure of intrinsically disordered and globular proteins 总被引:1,自引:0,他引:1
Hundertmark M Popova AV Rausch S Seckler R Hincha DK 《Biochemical and biophysical research communications》2012,417(1):122-128
Circular dichroism (CD) spectroscopy of five Arabidopsis late embryogenesis abundant (LEA) proteins constituting the plant specific families LEA_5 and LEA_6 showed that they are intrinsically disordered in solution and partially fold during drying. Structural predictions were comparable to these results for hydrated LEA_6, but not for LEA_5 proteins. FTIR spectroscopy showed that verbascose, but not sucrose, strongly affected the structure of the dry proteins. The four investigated globular proteins were only mildly affected by drying in the absence, but strongly in the presence of sugars. These data highlight the larger structural flexibility of disordered compared to globular proteins and the impact of sugars on the structure of both disordered and globular proteins during drying. 相似文献
117.
Petroi D Popova B Taheri-Talesh N Irniger S Shahpasandzadeh H Zweckstetter M Outeiro TF Braus GH 《The Journal of biological chemistry》2012,287(33):27567-27579
Parkinson disease is the second most common neurodegenerative disease. The molecular hallmark is the accumulation of proteinaceous inclusions termed Lewy bodies containing misfolded and aggregated α-synuclein. The molecular mechanism of clearance of α-synuclein aggregates was addressed using the bakers' yeast Saccharomyces cerevisiae as the model. Overexpression of wild type α-synuclein or the genetic variant A53T integrated into one genomic locus resulted in a gene copy-dependent manner in cytoplasmic proteinaceous inclusions reminiscent of the pathogenesis of the disease. In contrast, overexpression of the genetic variant A30P resulted only in transient aggregation, whereas the designer mutant A30P/A36P/A76P neither caused aggregation nor impaired yeast growth. The α-synuclein accumulation can be cleared after promoter shut-off by a combination of autophagy and vacuolar protein degradation. Whereas the proteasomal inhibitor MG-132 did not significantly inhibit aggregate clearance, treatment with phenylmethylsulfonyl fluoride, an inhibitor of vacuolar proteases, resulted in significant reduction in clearance. Consistently, a cim3-1 yeast mutant restricted in the 19 S proteasome regulatory subunit was unaffected in clearance, whereas an Δatg1 yeast mutant deficient in autophagy showed a delayed aggregate clearance response. A cim3-1Δatg1 double mutant was still able to clear aggregates, suggesting additional cellular mechanisms for α-synuclein clearance. Our data provide insight into the mechanisms yeast cells use for clearing different species of α-synuclein and demonstrate a higher contribution of the autophagy/vacuole than the proteasome system. This contributes to the understanding of how cells can cope with toxic and/or aggregated proteins and may ultimately enable the development of novel strategies for therapeutic intervention. 相似文献
118.
Gap junctions (GJs) are composed of membrane proteins that form channels connecting the cytoplasm of adjacent cells and permeable to ions and small molecules. They are considered to be the main or only type of intercellular channels and a universal feature of all multicellular animals (Metazoa). Till recently, sea anemones and corals (Anthozoa, Cnidaria) appeared to be an exception from this rule. There were no structural or physiological data supporting the presence of GJ in Anthozoa. For some time no genes homologous to GJ proteins (connexins or pannexins) were detected in sea anemone Nematostella vectensis (Cnidaria, Anthozoa) or other Anthozoa genomes. Recently, pannexin homolog was found in Nematostella. Our intracellular recordings demonstrate electrical coupling between blastomeres in embryos at the 8-cells stage. At the same time, carboxyfluorescein fluorescent dye did not diffuse between electrically coupled cells, which excludes the possibility that the observed electrical coupling is mediated by incomplete cytoplasm separation during the cleavage. These data support the idea that GJ are ubiquitous for Metazoa, and pannexins are universal GJ proteins. 相似文献
119.
A.?A.?AgarkovEmail author T.?N.?Popova L.?V.?Matasova 《Biochemistry (Moscow) Supplemental Series B: Biomedical Chemistry》2012,6(3):231-236
The effect of melatonin on the intensity of free radical processes and activities of superoxide dismutase (SOD, EC 1.15.1.1.)
and catalase (EC 1.11.1.6) has been investigated in liver and blood serum of rats with type II diabetes mellitus. According
to results of this study the development of diabetes was accompanied by the increase in biochemiluminescence parameters and
the enzyme activities studied. Melatonin administration changed the parameters studied towards control values and this is
obviously associated with realization of the antioxidant potential of this hormone. 相似文献
120.