Catalyzes the phosphorylation of adenosine to adenosine monophosphate (AMP). Can also catalyze the phosphorylation of the adenosine analog 2-methyladenosine (methyl-Ado) to methyl-AMP, the first step in the metabolism of this compound to an active form that displays antitubercular activity. Is not active on guanosine, inosine, deoxyadenosine, cytidine, uridine, or thymidine. Prefers dGTP and GTP to ATP as phosphate donors in vitro. adenosine + ATP = ADP + AMP + H(+) adenosine + GTP = AMP + GDP + H(+) adenosine + dGTP = AMP + dGDP + H(+) The enzyme is subject to substrate inhibition by adenosine and is competitively inhibited by the adenosine analog iodotubercidin. Unlike other adenosine kinases it is not stimulated by inorganic phosphate. Activity is stimulated in the presence of potassium, resulting in a 13- and 300-fold increase in the catalytic efficiency with adenosine and methyl-Ado as substrate, respectively; the stimulatory effects are not observed in the presence of NaCl or LiCl. GTP and dGTP are the best phosphate donors, with 2.5 and 4.7 times the activity observed with ATP, respectively. UTP, dATP, and dTTP exhibit about 33% of the activity observed with ATP, while CTP and dCTP are the worst phosphate donors, with 1.7 and 0.2% of the activity observed with ATP, respectively. Since K(+) exists at millimolar levels within cells, stimulation by K(+) is physiologically relevant, and kinetic values obtained in the presence of K(+) more closely reflect the true physiological state of the enzyme than values obtained in the absence of K(+). Optimum pH is 8-11. Activity decreases rapidly at values above pH 11 and below pH 8. Is inactive at pH 4.3. Purine metabolism; AMP biosynthesis via salvage pathway; AMP from adenosine: step 1/1. Homodimer. Belongs to the carbohydrate kinase PfkB family.