kinetics of reactivation of rabbit muscle aldolase after denaturation and dissociation in various solvent media

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Abstract
The denaturation of aldolase from rabbit muscle in various solvents leads to significant qualitative and quantitative differences with respect to the structural disintegration of the enzyme. The differences refer to the quaternary structure and to the conformation which is changed only slightly in MgCl2 while in guanidine · HCl or urea at pH ∼ 2 the molecule is close to the state of the random coil. Using the enzymic activity as a quantitative measure for the refolding process, the reaction order and the rate constants of the processes of structure formation (θ i → N*) are found to be identical. This observation suggests a common intermediate D in the process of renaturation after denaturation and dissociation in the different solvent media. D may be considered an intermediate state with a defined number of nucleation centers whose rapid formation is predetermined by the aminoacid sequence. As taken from the first order kinetics in the given range of enzyme concentration, transconformation reactions are rate limiting in the obligatory pathway of refolding. At low enzyme concentrations second order steps gain importance which indicates that the enzymic activity is significantly modified by the formation of the native quaternary structure.