[Mechanism of post-synthetic changes in glucose-6-phosphate dehydrogenase in human cells cultured in vitro]. / Mekhanizm postsinteticheskoi modifikatsii gliukozo-6- fosfatdegidrogenazy v kletkakh cheloveka, kul'tiviruemykh in vitro.

The reasons for the decreased stability of glucose-6-phosphate dehydrogenase in transformed human cells were investigated. The enzyme stability was found to be dependent on its subunit composition; the dimeric form possessed a lower stability in comparison with the tetrameric one. An addition of NADP to cell extracts which had partly lost their glucose-6-phosphate dehydrogenase activity, resulted in reactivation and stabilization of the enzyme. The constants for a forward (k1) and back (k2) reactions during stabilization are equal to 2.87 X 10(-3) and 5.77 X 10(-1) s-1, respectively. The inactivation and reactivation kinetics suggest that the enzyme destabilization may also occur inside the cells. The cells contain more than 40% of glucose-6-phosphate dehydrogenase molecules in an inactive form. A mechanism of destabilization and inactivation of glucose-6-phosphate dehydrogenase is proposed, which consists in NADP hydrolysis and enzyme decomposition to inactive monomers which are less stable to proteolysis.

[Secondary structure of RNA of influenza virus in free form and in ribonucleoprotein]. / Izuchenie vtorichnoi struktury RNK virusa grippa v svobodnom sostoianii i v sostave ribonukleoproteidov.

Large amounts of RNA and RNP isolated from influenza virus were obtained. This has allowed us to undertake detailed physical studies of the secondary structure of RNA of influenza virus in free form and in RNP. Analysis of CD spectrum and the hypochromic effect after thermal denaturation of RNA indicated that RNA in free form contains 58--62% double-stranded regions. By comparative studies of the secondary structure of RNA in RNP, it was estimated that 12--14% of the RNA exists in double-stranded form.