The AK5 gene encodes an enzyme belonging to the adenylate kinase family. Specifically, AK5 is a nucleoside monophosphate (NMP) kinase that is responsible for the phosphorylation state of intracellular adenine nucleotide. Substrate specificity is determined by the phosphate donor; AK5 phosphorylates AMP and dAMP when ATP is the donor, while it acts on AMP, CMP and dCMP when GTP is the donor. The enzyme is localized to the cytosol and is made up of two 2 catalytic adenylate kinase domains known as AK5p1 and AK5p2. Both domains consist of a glycine-rich p-loop, an NMP-binding domain, and a LID domain.
Recent studies have shed light on the pathological effect of AK5 mutations. The gene has been suspected to play a role in haemolytic anemia as well as in autoimmune-mediated limbic encephalitis.