[Effect of specific ligands on heat inactivation of muscle glycogen phosphorylase b].
It has been shown that the rate constant, k, for thermal inactivation of rabbit skeletal muscle glycogen phosphorylase b decreases as the enzyme concentration increases. This effect is interpreted within the framework of a kinetic model which includes two parallelly occurring processes, namely: phosphorylase b denaturation in solution and denaturation of the enzyme absorbed on test-tube walls. The contribution of the latter process increases with a decrease in the enzyme concentration. The protective effect of the allosteric activator (AMP), allosteric inhibitors (glucose 6-phosphate and FMN) and the competitive inhibitor (glucose) against heat denaturation of glycogen phosphorylase b has been demonstrated. Quantitative analysis of the dependence of the rate constant, k, on concentration of AMP, glucose 6-phosphate and FMN allows the calculation of microscopic constants for dissociation of phosphorylase b complexes with these ligands for the given experimental conditions as equal to 0.34, 0.50 and 0.30 mM, respectively. The S-shaped dependence of the rate constant of thermal inactivation on glucose concentration points to the existence of positive cooperative interactions between glucose-binding sites in the dimeric molecule of phosphorylase b (nH = 1.8).
Kornilaev
B A
BA
Kurganov
B I
BI
Eronina
T B
TB
Livanova
N B
NB
D000494:Allosteric Regulation; D000818:Animals; D006358:Hot Temperature; D007700:Kinetics; D008024:Ligands; D018482:Muscle, Skeletal / Q000201:enzymology*; D010763:Phosphorylase b / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011489:Protein Denaturation; D011817:Rabbits; D013379:Substrate Specificity
D008024:Ligands; D010763:Phosphorylase b
Vliianie spetsificheskikh ligandov na teplovuiu inaktivatsiiu myshechnoĭ glikogenfosforilazy b.