Creatine kinase (CK), is an enzyme expressed by various tissues and cell types. CK catalyses the conversion of creatine and consumes adenosine triphosphate (ATP) to create phosphocreatine and adenosine diphosphate (ADP). In the cells, the cytosolic CK enzymes consist of two subunits, which can be either B (brain type) or M (muscle type). There are, therefore, three different isoenzymes: CK-MM, C kbB and CK-MB. . Alternative Names: CK-MM protein, Creatine Kinase-MM Isoenzyme Protein