Macro-Creatine Kinase-BB: Observations on 6 Patients

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Abstract
From 2000 sera with elevated total creatine kinase activity the sera of 6 patients showed a persistent high and anamnestically inexplicable creatine kinase activity level. The serum isoenzyme pattern was analyzed by 4 different methods. Electrophoresis revealed an atypical creatine kinase activity band located between creatine kinase-MM and creatine kinase-MB. An adequate estimation of persistent enzyme activity could only be achieved by immunotitration (immunoprecipitation), which identified the creatine kinase activity as due primarily to the isoenzyme creatine kinase-BB. Other methods (immunoinhibition and column chromatography) may lead to misinterpretations. The atypical serum creatine kinase-BB showed a higher MW (250,000) and altered substrate affinity as compared to native creatine kinase-BB. Both properties are attributable to binding of creatine kinase-BB to immunoglobulins.