The Comparative Enzymology of Creatine Kinases

Four purified creatine kinases have been studied with respect to their s value, sedimentation equilibrium, and elution volume on gel filtration. These studies indicate that the creatine kinases all have approximately the same molecular weight, near 80,000. The chicken muscle enzyme at low pH in the presence of a reducing agent had a molecular weight one-half that of the native enzyme. On electrophoresis in starch gel the enzymes all migrated differently. The two creatine kinases from muscle (chicken and rabbit) remained near the origin while the brain enzymes (chicken and rabbit) migrated toward the cathode. The dissociation of the enzymes in urea has been studied; when two dissimilar enzymes are dissociated together in urea and allowed to recombine, both parent enzymes, plus a hybrid enzyme, are formed. Two moles of iodoacetate per mole of enzyme will inactivate the creatine kinases; p-hydroxymercuribenzoate will bind to the enzymes but upon dilution recovery of enzymic activity occurs. The results indicate that creatine kinase has a dimeric structure.