InterPro domain: IPR000850

Adenylate kinases (ADK) are phosphotransferases that catalyse the reversible reaction AMP + MgATP = ADP + MgADP an essential reaction for many processes in living cells. Two ADK isozymes have been identified in mammalian cells. These specifically bind AMP and favour binding to ATP over other nucleotide triphosphates (AK1 is cytosolic and AK2 is located in the mitochondria). A third ADK has been identified in bovine heart and human cells [ 1 ], this is a mitochondrial GTP:AMP phosphotransferase, also specific for the phosphorylation of AMP, but can only use GTP or ITP as asubstrate [ 2 ]. ADK has also been identified in different bacterial species and in yeast [ 3 ]. Two further enzymes are known to be related to the ADK family, i.e. yeast uridine monophosphokinase and slime mold UMP-CMP kinase. Within the ADK family there are several conserved regions, including the ATP-binding domains. One of the most conserved areas includes an Arg residue, whose modification inactivates the enzyme, together with an Asp that resides in the catalytic cleft of the enzyme and participates in a salt bridge.

In humans, nine different AK isoenzymes have been identified (AK1-9) [ 4 ].

1. The amino acid sequence of GTP:AMP phosphotransferase from beef-heart mitochondria. Extensive homology with cytosolic adenylate kinase. Eur. J. Biochem. 143, 331-9
2. Mitochondrial GTP-AMP phosphotransferase. 2. Kinetic and equilibrium dialysis studies. Eur. J. Biochem. 93, 263-7
3. A putative second adenylate kinase-encoding gene from the yeast Saccharomyces cerevisiae. Gene 114, 145-8
4. The human adenylate kinase 9 is a nucleoside mono- and diphosphate kinase. Int. J. Biochem. Cell Biol. 45, 925-31