Transformation of creatine kinase-BB isoenzyme in vitro: effect of carboxylic acids, thiols, pH, cations, and chelators.

Creatine kinase isoenzyme BB from rat brain was incubated with serum, dialyzed serum, or plasma, with added carboxylic acids, thiols, buffers, or cations. It was found to be very unstable at 37 degrees C under all these conditions, being transformed to CK-BB', a form that migrates like CK-MB on agarose electrophoretic plates. This transformation is enhanced at alkaline pH and, especially, by Zn2+. CK-BB' is quite stable, and probably results from binding of cations to CK-BB, because the transformation is prevented by EDTA and citrate.