Creatine kinases (CK) are a large family of isoenzymes that regulate levels of ATP in subcellular compartments, where they provide ATP at sites of fluctuating energy demand by the transfer of phosphates between creatine and adenine nucleotides. CKs provide the energy of phosphate hydrolysis necessary to drive the normal function of many cellular systems. 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. This MAb recognizes the CKBB isoenzyme and does not react with the B subunit in CKMB.