Аннотация:Phosphorylase kinase (PhK; EC 2.7.1.38) plays a key role in the regulation of glycogen metabolism in skeletal muscle. PhK with molecular mass of 1320 kDa has a complex molecular organization. The PhK molecule consists of four subunits that form a hexadecamer ()4, where the -subunit possesses the catalytic activity and other subunits regulate its activity. Ca2+and Mg2+ions stimulate PhK activity by inducing changes in the tertiaryand quaternary structure of the molecule and also stimulate association/aggregation of PhK hexadecamer molecules. Ca2+-free PhK and PhK molecules in the presence of Ca2+and Mg2+ionshave different conformations and physicochemical properties. The kinetics of association/aggregation of PhK from rabbit skeletal muscle was studied at 40°C, close to the average physiologicaltemperature of the rabbit, using dynamic light scattering (40 mM Hepes, pH 6.8; 0.1 mM Ca2+, 10 mM Mg2+, 0.1 M NaCl). The initial rate of aggregation was calculated from the kinetic curvesdescribing an increase in the light scattering intensity with time.Based on the analysis of the initial rate of aggregation, depending on the initial concentration of the protein, it has been concluded that the order of aggregation with respect to protein is equal to unity. Thus, the rate-limiting stage of heat-induced aggregation of PhK under used conditions Is the stage of unfolding of theprotein molecule. Construction of a plot showing the relationship between the light scattering intensity and hydrodynamic radius (Rh) of protein aggregates indicates that the initial stage of PhK aggregation is the stage of formation of the start aggregates. Itwas shown that the hydrodynamic radius of start aggregates formed at PhK concentration of 0.1 mg/mL is 29 nm and increased to 56 nm at [PhK]=0.8 mg/mL.This work was funded by the Russian Science Foundation (grant 16-14-10055).