Publications

• Structure of human adenosine kinase at 1.5-A resolution.

  Mathews I.I., Erion M.D., Ealick S.E.

  Adenosine kinase (AK) is a key enzyme in the regulation of extracellular adenosine and intracellular adenylate levels. Inhibitors of adenosine kinase elevate adenosine to levels that activate nearby adenosine receptors and produce a wide variety of therapeutically beneficial activities. Accordingl ... >> More

  Adenosine kinase (AK) is a key enzyme in the regulation of extracellular adenosine and intracellular adenylate levels. Inhibitors of adenosine kinase elevate adenosine to levels that activate nearby adenosine receptors and produce a wide variety of therapeutically beneficial activities. Accordingly, AK is a promising target for new analgesic, neuroprotective, and cardioprotective agents. We determined the structure of human adenosine kinase by X-ray crystallography using MAD phasing techniques and refined the structure to 1.5 A resolution. The enzyme structure consisted of one large alpha/beta domain with nine beta-strands, eight alpha-helices, and one small alpha/beta-domain with five beta-strands and two alpha-helices. The active site is formed along the edge of the beta-sheet in the large domain while the small domain acts as a lid to cover the upper face of the active site. The overall structure is similar to the recently reported structure of ribokinase from Escherichia coli [Sigrell et al. (1998) Structure 6, 183-193]. The structure of ribokinase was determined at 1.8 A resolution and represents the first structure of a new family of carbohydrate kinases. Two molecules of adenosine were present in the AK crystal structure with one adenosine molecule located in a site that matches the ribose site in ribokinase and probably represents the substrate-binding site. The second adenosine site overlaps the ADP site in ribokinase and probably represents the ATP site. A Mg2+ ion binding site is observed in a trough between the two adenosine sites. The structure of the active site is consistent with the observed substrate specificity. The active-site model suggests that Asp300 is an important catalytic residue involved in the deprotonation of the 5'-hydroxyl during the phosphate transfer. << Less

  Biochemistry 37:15607-15620(1998) [PubMed] [EuropePMC]

• Identification and characterization of a unique adenosine kinase from Mycobacterium tuberculosis.

  Long M.C., Escuyer V., Parker W.B.

  Adenosine kinase (AK) is a purine salvage enzyme that catalyzes the phosphorylation of adenosine to AMP. In Mycobacterium tuberculosis, AK can also catalyze the phosphorylation of the adenosine analog 2-methyladenosine (methyl-Ado), the first step in the metabolism of this compound to an active fo ... >> More

  Adenosine kinase (AK) is a purine salvage enzyme that catalyzes the phosphorylation of adenosine to AMP. In Mycobacterium tuberculosis, AK can also catalyze the phosphorylation of the adenosine analog 2-methyladenosine (methyl-Ado), the first step in the metabolism of this compound to an active form. Purification of AK from M. tuberculosis yielded a 35-kDa protein that existed as a dimer in its native form. Adenosine (Ado) was preferred as a substrate at least 30-fold (Km = 0.8 +/-0.08 microM) over other natural nucleosides, and substrate inhibition was observed when Ado concentrations exceeded 5 micro M. M. tuberculosis and human AKs exhibited different affinities for methyl-Ado, with Km values of 79 and 960 microM, respectively, indicating that differences exist between the substrate binding sites of these enzymes. ATP was a good phosphate donor (Km = 1100 +/-140 microM); however, the activity levels observed with dGTP and GTP were 4.7 and 2.5 times the levels observed with ATP, respectively. M. tuberculosis AK activity was dependent on Mg2+, and activity was stimulated by potassium, as reflected by a decrease in the Km and an increase in Vmax for both Ado and methyl-Ado. The N-terminal amino acid sequence of the purified enzyme revealed complete identity with Rv2202c, a protein currently classified as a hypothetical sugar kinase. When an AK-deficient strain of M. tuberculosis (SRICK1) was transformed with this gene, it exhibited a 5,000-fold increase in AK activity compared to extracts from the original mutants. These results verified that the protein that we identified as AK was coded for by Rv2202c. AK is not commonly found in bacteria, and to the best of our knowledge, M. tuberculosis AK is the first bacterial AK to be characterized. The enzyme shows greater sequence homology with ribokinase and fructokinase than it does with other AKs. The multiple differences that exist between M. tuberculosis and human AKs may provide the molecular basis for the development of nucleoside analog compounds with selective activity against M. tuberculosis. << Less

  J. Bacteriol. 185:6548-6555(2003) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• The enzymatic synthesis of adenylic acid; adenosinekinase.

  CAPUTTO R.

  J Biol Chem 189:801-814(1951) [PubMed] [EuropePMC]

• Enzymatic phosphorylation of adenosine and 2,6-diaminopurine riboside.

  KORNBERG A., PRICER W.E. Jr.

  J Biol Chem 193:481-495(1951) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.