Reversibly catalyzes the transfer of phosphate between ATP and various phosphogens (e.g. creatine phosphate). 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 (By similarity). ATP + creatine = ADP + H(+) + N-phosphocreatine Exists as an octamer composed of four CKMT2 homodimers. Mitochondrial creatine kinase binds cardiolipin. Belongs to the ATP:guanido phosphotransferase family.