Catalyzes the phosphorylation of ribose at O-5 in a reaction requiring ATP and magnesium. The resulting D-ribose-5-phosphate can then be used either for sythesis of nucleotides, histidine, and tryptophan, or as a component of the pentose phosphate pathway (By similarity) (PubMed:27601466). Can also use xylose and fructose as carbohydrate substrates with a low efficiency (PubMed:27601466). Can use GTP, and, to a lower extent, CTP and UTP as alternative phosphoryl donors (PubMed:27601466). ATP + D-ribose = ADP + D-ribose 5-phosphate + H(+) Requires a divalent cation, most likely magnesium in vivo, as an electrophilic catalyst to aid phosphoryl group transfer. It is the chelate of the metal and the nucleotide that is the actual substrate. Activated by a monovalent cation that binds near, but not in, the active site. The most likely occupant of the site in vivo is potassium. Ion binding induces a conformational change that may alter substrate affinity (By similarity) (PubMed:27601466). Repressed by calcium, rubidium and sodium (PubMed:27601466). Substrate inhibition is observed in the presence of high ATP concentration (Ki=2.44 mM) (PubMed:27601466). kcat is 2 sec(-1). Carbohydrate metabolism; D-ribose degradation; D-ribose 5-phosphate from beta-D-ribopyranose: step 2/2. Homodimer. Abnormal accumulation of D-ribose. D-ribose hypersensitivity; normal growth except in the presence of D-ribose, which leads to chlorosis and growth inhibition. Belongs to the carbohydrate kinase PfkB family. Ribokinase subfamily. Cleavage site of the transit peptide is likely localized before the predicted cleavage site at Val-74, probably around His-67. Truncated N-terminus.