Cytosolic creatine kinase catalyzes the reaction of creatine and ATP to form phosphocreatine and ADP. The active form of the enzyme is a dimer. Monomers of the cytosolic enzyme occur in two isoforms, B and M, so called because of their abundance in brain and muscle respectively. The enzyme is widely expressed in the body and many tissues express both isoforms. Both homo- (BB, MM) and heterodimers (BM) are catalytically active.
Merz KM, Jr,
creatine kinase activity of CKB, CKM [cytosol]