Effects of pH,albumin and urate on the inactivation profile of rabbit muscle creatine phosphokinase.

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Abstract
The effects of pH, albumin and urate on the inactivation behavior of rabbit muscle creatine phosphokinase (CPK) were investigated at 39.degree. C. The conditions under which the inactivation of CPK shows apparent first order kinetics and biphasic behavior were explored and regression equations are presented along with half-lives. A circular dichroism (CD) study showed no evidence of spectral change of CPK in the range of pH 6.00-8.00, and a kinetic study showed that CPK is most stable at near neutral pH. Both rabbit serum albumin (RSA) and urate significantly enhance the stability of the CPK activity and retard CPK coagulation during incubation. No evidence for any intermolecular interactions between RSA and CPK in pH 7.40, 50 mM phosphate buffer solution was obtained in the CD study. CPK is presumably just dispersed in the matrices of RSA and stabilized by protein colloid. On the other hand, urate is likely to form a polymeric structure in the buffer at around the physiological urate level in circulatory blood (2.5-3.5 .times. 10-4 M). CD spectra of CPK can be observed with a maximum around 287 nm, induced by urate. The molar ellipticity coefficient depends on the concentration of urate present in the solution.