[Effect of temperature on the kinetics of the phosphorylase reaction and phosphorylase activation induced by phosphorylase kinase in the skate Dasyatis pastinaca].

The dependence of the phosphorylation reaction rate on the glucose-1-phosphate concentration is investigated in Dasyatis pastinaca in a wide temperature range (5-45 degrees C). In the temperature range of 20-40 degrees C nH is equal to 1.3-1.7. The disturbance of allosteric interactions of active sites with the loss of kinetic substrate cooperativity is observed at 45 degrees C. v(S)-Dependence with the intermediate plateau is obtained at 5 degrees C and high concentration of glycogen phosphorylase B (EC 2.4.1.1), that is explained by the formation of inactive tetramer. Studies in activation of glycogen phosphorylase B of Dasyatis pastinaca under the effect of glycogen phosphorylase (EC 2.7.1.38) kinase have revealed temperature-dependent changes in the pattern of kinetic curve. An assumption is advanced that the presence of the association-dissociation equilibrium in oligomeric forms of glycogen phosphorylase B with different enzymic activity and the effect of the temperature-dependent conformation state of this enzyme on the kinase reaction rate plays an essential role in regulation of glycogenolysis in the muscular tissue of ectothermal animals.