Biochemical differences between the MB and MM isoenzymes of creatine kinase.

The biochemical properties of partially purified preparations of human myocardial MB and MM iosenzymes of creatine kinase have been compared with one another. Differences in substrate affinity, behaviour with inhibitors, and heat denaturation have been demonstrated. It is doubtful if the differences we have shown are sufficiently great to form the basis of a practical routine procedure for measuring serum levels of the MB isoenzyme.