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. This is the function of CKMT2 (creatine kinase, mitochondrial 2, Ensembl gene identifier ENSG00000131730).