[Interaction of hexokinase II isoenzyme from rat skeletal muscles with lecithin liposomes].
It was found that in the presence of Mg2+ (pH 7.5) rat skeletal muscle hexokinase isozyme II is firmly adsorbed on mitochondrial and artificial phospholipid membranes (lecithin liposomes). In both cases the adsorption isotherm has similar quantitative and qualitative characteristics, which points to the absence of specific binding sites on the membranes. Under these conditions, immobilization of hexokinase on various membranes is concomitant with similar changes in the enzyme stability upon storage as well as with the pH-dependence of the enzyme activity. It was demonstrated that the bound hexokinase form has a greater value of V, an increased affinity for glucose and a decreased sensitivity to the inhibitory action of glucose-6-phosphate as compared to the free form. Besides, this form is in a greater degree subjected to the inhibitory influence of ADP with respect to glucose. In this case, the enzyme affinity for ATP and the Ki value for ADP with respect to ATP is practically the same both for the free and membrane-bound forms. The data obtained suggest that the phospholipid component of mitochondrial membranes participates in the enzyme binding in the presence of Mg2+. It was assumed that the model system used in the present study, i.e., hexokinase-Mg2+-liposomes, may be successfully used for the analysis of an adsorption mechanism of regulation of hexokinase activity in the cell.
D000327:Adsorption; D000818:Animals; D004789:Enzyme Activation; D006593:Hexokinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes / Q000032:analysis*; D008931:Mitochondria, Muscle / Q000201:enzymology / Q000378:metabolism; D009132:Muscles / Q000201:enzymology*; D010713:Phosphatidylcholines; D051381:Rats
D007527:Isoenzymes; D008081:Liposomes; D010713:Phosphatidylcholines; D006593:Hexokinase
Vzaimodeĭstvie izozima II geksokinazy skeletnykh myshts krysy s letsitinovymi liposomami.