Ukrains'kyi biokhimichnyi zhurnal最新文献

The protein-synthetizing activity in postmitochondrial supernatant (S15) was studied as affected by ethylene glycol, PEG-400, PEG-4000, DMSO, ethanol, methanol, and glycerol. It is found that cryoprotectants inhibit 14C-leucine incorporation in the presence of physiological concentrations of Mg2+ (5 mM) in the cell-free system. All cryoprotectants, exept of glycerol, shift the maximum of 14C-leucine incorporation towards lower Mg2+ concentrations in the cell-free system.

The content of soluble fractions and biosynthesis intensity of collagen were studied by means of 3H-proline incorporation into the lung tissues of different-age rats. The method with incorporation of a radioactive label is shown to detect more clearly the age peculiarities in collagen metabolism. The most considerable decrease in the intensity of 3H-proline incorporation into lung collagen is observed during the first four months of the rat life.

The quaternary structure and some kinetic properties were studied for NAD-kinase from the rabbit skeletal muscles. The molecular weight of the 150-300-fold purified enzymic preparation was determined by separation in the Sephadex G-200 thin layer, by means of Sephadex G-200 column gel-filtration and by the method of electrophoresis in the gradient of polyacrylamide gel concentration. Some molecular forms of NAD-kinase with a molecular weight of 31000-305000 are found in the enzymic preparation and possibility to change from one form to another is shown. On the basis of the established quaternary structure and complex kinetic characteristics of the enzyme a conclusion is drawn on the existence of the rabbit skeletal muscle NAD-kinase as an equilibrium system of the oligomeric forms possessing different catalytic activity and consisting of different combinations of subunits with a molecular weight of 31000.

Activity of hexokinase, phosphorylase, glucoso-6-phosphate dehydrogenase lactate-dehydrogenase was studied in liver slices, homogenate and supernatant fraction after freezing at a rate of 1 degree/min down to -30 degrees C. The enzyme activity in homogenate and supernatant fraction does not change after freezing. A significant reduction in the activity of most enzymes that is followed by an increase in their activity in the freezing medium was observed in the experiments. Cryoprotectant polyethylene glycol, mol. wt. 300 and 1,000 (PEG-300 and PEG-1,000), partially prevents the observed changes in the enzyme activity; PEG-1,000 is more effective than PEG-300. Experimental results show that the main reason for the reduction of the enzyme activity observed after freezing the tissue slices is a decrease in the volume of intracellular enzyme proteins due to their leakage from the injured cellular elements into the exocellular medium.

The mechanisms were studied determining the protein synthesis intensification in the skeletal muscles of albino rats during systematic physical activity only and in combination with enteroadministration of amino acid mixture. It is shown that systematic physical activity induces an increase in the RNA content in the skeletal muscles along with the lack of differences in specific radioactivity of microsomal, ribosomal and poly-A-containing mRNA. Supplementary administration of amino acid mixture in combination with the systematic physical activity induces a further increase in the skeletal muscle RNA content along with a decrease in specific radioactivity of poly-A-containing mRNA, parallel with an increase in its portion in microsomal RNA, as well as results in shifts of the ribosomal spectrum towards polysomal complexes.

Adenine- and uridine di- and triphosphates (in a 3 mM concentration) increase considerably phosphoprotein phosphatase (PPPase) (EC 3.1.3.16) activity of rat and chicken myocardium homogenates. AMP and Pi are effective inhibitors of the enzyme. The ATP activating effect is also shown in partially purified preparations of rat myocardium PPPase. ATP is able of protecting significantly the enzyme during its thermodenaturation.

Protein kinase from the bull myocardium tissue was separated by means of the stepped gradient of buffer concentrations on DEAE-cellulose. Sensitivity of the obtained fractions to cAMP was studied. Protein kinase isolated at elution by 0.3 M potassium-phosphate buffer from DEAE-cellulose is less sensitive to cAMP than protein kinase isolated according to Kuo. A decrease in the content of cAMP is established in the tissues of the skeletal muscles and adrenals of rats after long physical loading. No statistically significant changes are found in the level of cAMP under the same conditions in the myocardium and brain tissues.

The activity of monoaminoxidase (MAO) and the amount of catecholamines (CA) were studied in the heart, brain and liver of adrenalectomized and demedullated rats. Adrenalectomy increased the MAO activity of the brain and heart homogenates but had no effect on that of the liver mitochondria. The level of liver mitochondria MAO does not change when rats were demedullated, in this case there is some reduction in the content of the so-called PO (substances with the affinities of CA chinoid oxidation product). Neither adrenalectomy nor demedullation affect the amount of CA of all the studied tissues.

Str. griseus protease hydrolyzes essentially insoluble collagen of bone tissue, with 34.5% of protein solubilized and 6.0% of peptide bonds splitted. 60.0 M of N-terminal amino acids is formed per 10(5) g of protein, out of them 16.8 in the fraction of free amino acids, 32.3 M in the fraction of soluble DNP-peptides and 10.9 M in that of insoluble DNP-peptides. Under the effect of trypsin the amount of collagen changing to the soluble form is thrice as low and the splitted peptide bonds are ten times as low as in case of the Str. griseus protease action. The peptide bonds incorporating the N-end of serine, threonine, glycine are more available for protease. It is supposed that under used conditions Str. griseus protease hydrolyzes not only telepeptides but also the main molecule of collagen.

Metabolism of amino acids in the liver in connection with the adrenocortical functions of the adrenals was studied in rats as affected by 3-hour swimming. This load causes an increase in the content of corticosterone in blood, in the activity of alanine aminotranspherase as well as the decrease in the amount of free amino acids in the liver tissue. These changes are absent in adrenalectomized rats and appear again when corticosterone is administered to adrenalectomized animals before swimming.