AK2(Adenylate kinase 2,mitochondrial ) is also named as ADK2 and belongs to the adenylate kinase family. It plays a unique role in energy metabolism and energy transfer by regulating the ATP/ADP rate between the cytoplasma matrix and the mitochondria and it is increased expression during adipocyte and B cell differentiation. AK2 catalyzes the reversible transfer of a phosphoryl group from ATP to AMP. Defects in AK2 are the cause of reticular dysgenesis (RDYS). It has 6 isoforms produced by alternative splicing.