Identification of a novel human adenylate kinase - cDNA cloning, expression analysis, chromosome localization and characterization of the recombinantprotein

Adenylate kinases have an important role in the synthesis of adenine nucleo tides that are required for cellular metabolism. We report the cDNA cloning of a novel 22-kDa human enzyme that is sequence related to the human adeny late kinases and to UMP/CMP kinase of several species. The enzyme was expre ssed in Escherichia coli and shown to catalyse phosphorylation of AMP and d AMP with ATP as phosphate donor. When GTP was used as phosphate donor, the enzyme phosphorylated AMP, CMP, and to a small extent dCMP. Expression as a fusion protein with the green fluorescent protein showed that the enzyme i s located in the cytosol. Northern blot analysis with mRNA from eight diffe rent human tissues demonstrated that the enzyme was expressed exclusively i n brain, with two mRNA isoforms of 2.4 and 4.0 kb. The gene that encoded th e enzyme was localized to chromosome 1p31. Based on the substrate specifici ty and the sequence similarity with the previously identified human adenyla te kinases, we have named this novel enzyme adenylate kinase 5.