Creatine kinase M-type is also known as Creatine kinase M chain,M-CK. It is a protein that in humans is encoded by the CKM gene. It belongs to the ATP:guanido phosphotransferase family,containing 1 phosphagen kinase C-terminal domain and 1 phosphagen kinase N-terminal domain. Creatine kinase M-type can reversibly catalyzes the transfer of phosphate between ATP and various phosphogens. It plays a central role in energy transduction in tissues with large, fluctuating energy demands, such as skeletal muscle, heart, brain and spermatozoa.