Mitochondrial creatine kinase S-type (CKMT2, 57- fold) and U-type (CKMT1A, 18-fold) are responsible for the energy and metabolite transfer between mitochondria and cytoplasm (i.e. the creatine phosphate shuttle), and were increased in renal oncocytomas. This evidence concerns the gene CKMT1A and kidney oncocytoma.