CK is a dimeric enzyme. There are two common gene products, one coding for the subunit (so named because of its predominance in muscle) and the other for the B subunit (so named because of its predominance in brain tissue). The three common forms of active CK include two homodimers and one heterodimer. There is a third gene product which results in the mitochondrial form of CK. The CK isoenzymes have different isoelectric points and thus can be identified by electrophoresis.

CKBB is an important constituent of brain tissue, with measurement of CKBB in serum and other bodily fluids, a useful tool in the diagnosis and prognosis of brain pathologies. This includes physical injury, various types of cancer and neurodegenerative diseases such as Alzheimer’s disease and CJD.