Adenylate kinase (AK, adenosine triphosphate-adenosine monophosphate [ATP-AMP] phospho-transferase, EC 2.7.4.3) is a ubiquitous monomeric enzyme involved energy metabolism of prokaryotic and eukaryotic cells. Five isozymes of adenylate kinase have been identified in vertebrates. AK1 is present in the cytosol of skeletal muscle, brain, and erythrocyte, while AK2 is localized in the intermembrane space of mitochondria of liver, kidney, spleen and heart. AK3, called GTP:AMP phosphotransferase, exists in the mitochondrial matrix of liver and heart. These isozymes contribute to homeostasis of the adenine nucleotide composition in the cell. Recombinant human AK3, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques. Synonyms: AK3, AKL3L, Adenylate kinase 3 alpha like 1, Adenylate kinase 3, AK3L1, AK6, AKL3L1, FIX, RP11 6J24.4. NCBI no.: NP_982289