Studies on interaction of phosphorylase kinase from rabbit skeletal muscle with glycogen in the presence of ATP and ADP.

The influence of ATP on complex formation of phosphorylase kinase (PhK) with glycogen in the presence of Ca(2+) and Mg(2+) has been studied. The initial rate of complex formation decreases with increasing ATP concentration, the dependence of the initial rate on the concentration of ATP having a cooperative character. Formation of the complex of PhK with glycogen in the presence of ATP occurs after a lag period, which increases with increasing ATP concentration.

Phosphorylation of the alpha-subunit of Na,K-ATPase from duck salt glands by cAMP-dependent protein kinase inhibits the enzyme activity.

Although it was shown earlier that phosphorylation of Na,K-ATPase by cAMP-dependent protein kinase (PKA) occurs in intact cells, the purified enzyme in vitro is phosphorylated by PKA only after treatment by detergent. This is accompanied by an unfortunate side effect of the detergent that results in complete loss of Na,K-ATPase activity. To reveal the effect of Na,K-ATPase phosphorylation by PKA on the enzyme activity in vitro, the effects of different detergents and ligands on the stoichiometry of the phosphorylation and activity of Na,K-ATPase from duck salt glands (alpha1beta1-isoenzyme) were comparatively studied.

Phosphorylation of lactate dehydrogenase by protein kinases.

The influence of phosphorylation on the properties of lactate dehydrogenase (LDH) has been studied. Data obtained using the immobilization approach support the assumption that the autophosphorylation of LDH discovered previously in the presence of ATP has no relation to protein kinase activity of the enzyme. Phosphorylation of native LDH by tyrosine kinases was shown to be inefficient.

Antitumor activity of alpha fetoprotein and epidermal growth factor conjugates in vitro and in vivo.

Conjugates of carminomycin (Cm) with alpha-fetoprotein (AFP) and epidermal growth factor (EGF) were prepared and their cytotoxic activities were studied in vitro. Both conjugates showed cytotoxic activity which exceeded that of free Cm in tumor cell cultures of MCF-7, SKOV3, QOS, P388 and B16 cells. The antitumor effects of the conjugates were studied in vivo in mice with subcutaneous tumors of B16 and P388 cells.