Catalyzes the phosphorylation of a wide range of nucleosides to yield nucleoside monophosphates. Shows the highest activity for inosine, guanosine and cytidine, but very poor kinase activity with adenosine, thymidine, uridine and xanthosine. ATP is the best phosphate donor, but can also use ITP and GTP. Shows extremely low activity with fructose-6-phosphate. ATP + cytidine = ADP + CMP + H(+) ATP + guanosine = ADP + GMP + H(+) ATP + inosine = ADP + H(+) + IMP Can use Mg(2+) and Mn(2+) with equal efficiency in vitro, and to a lesser extent, Ni(2+). Optimum pH is 7.0. 50% of activity is found at pH 6.1 and 8.2. Optimum temperature is 85 degrees Celsius. Thermostable. Homodimer. Belongs to the carbohydrate kinase PfkB family.