Rapid Purificationof Creatine Kinase MB lsoenzymeon PreparativePolyacrylamideSlabs

We describe a procedure for purification of creatine kinase (EC 2.7.3.2) MB isoenzyme (CK-MB) from human cardiac muscle by preparative electrophoresis on polyacrylamide gel. From a 50-g portion of human myocardium we isolated 21 mg of CK-MB, which had a specific creatine kinase activity of 405 kU/g. The CK-MB exhibited an enzyme band on polyacrylamide gel electrophoresis (PAGE) with staining for enzyme activity. The preparation showed single protein bands on sodium dodecyl SUlfate-PAGE, pore gradient electrophoresis, and isoelectric focusing electrophoresis, the relative molecular masses of the subunit and of the whole enzyme being 43 000 and 86 000, respectively, and the isoelectric point being 5.0. In addition, the purified CK-MB showed desirable immunological specificity and affinity (K = 2.4 x lOll L’mol) when measured by radioimmunoassay.