Creatine kinase isoenzymes: their separation and quantitation.

The cardiospecificity of the MB isoenzyme of creatine kinase, EC 2.7.3.2, (CK) with its associated diagnostic and research value has resulted in the development of a number of procedures for the separation and quantitation of the three isoenzymes of CK. In our experience methods involving cellulose acetate electrophoresis, apposition incubation, and fluoroscanning for quantitation are of limited linearity, insensitive, and irreproducible. We have, therefore, developed a method which overcomes these difficulties. Our method is based on agarose gel electrophoresis, gel overlay incubation with optimisation of all substrates and elution of the NADPH into solution for isoenzyme quantitation. We have: (1) characterised this technique; (2) used it to verify the extent to which the MB isoenzyme of CK is cardiospyocardial; (3) studied its application to the diagnosis of acute myocardial infarction; and (4) compared it with existing methods involving dithiothreitol activation and ion exchange chromatography.