Creatine kinase plays a key role in the energy metabolism of cells with intermittently high and fluctuating energy requirements. Examples of such cells include cardiac or skeletal muscle cells and neural tissues of brain and retina. The enzyme catalyzes the reversible transfer of the phosphoryl group from phosphorylcreatine to ADP, in order to generate ATP.1 The molecular mass of the protein is found to be approximately 80 kDa Da. It is made up of 2 subunits, each having a molecular weight of 40 kDa ± 2000. The lighter subunit is present in larger amounts.http://www.creative-enzymes.com/product/Native-Rabbit-Creatine-Phosphokinase_1113.html