Creatine Kinase MB consists of a dimer of nonidentical chains. With MM being the major form in skeletal muscle and myocardium, MB existing in myocardium, and BB existing in many tissues, especially brain. Creatine Kinase MB reversibly catalyses the transfer of phosphate between ATP and various phosphogens. The creatine kinase isoenzymes play a central role in energy transduction in tissues with large fluctuating energy demands such as skeletal muscle, heart, brain and spermatozoa. Creatine phosphokinase, also known as 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 cells, the "cytosolic" CK enzymes consist of two subunits, which can be either B (brain type) or M (muscle type). There are three different isoenzymes: CKMM, CKBB and CKMB.Synonyms: CK-MB, Creatine Kinase MB