In order for D-ribose to be incorporated into ATP or other high energy phosphorylated derivatives, ribose must first be converted into ribose-5-phosphate (R5P), which can then be used either for sythesis of nucleotides, histidine, and tryptophan, or as a component of the pentose phosphate pathway. Cytosolic ribokinase (RBKS) catalyses this reaction in the presence of ATP (Park et al. 2007). Other pentoses and simple sugars were either not or poorly phosphorylated by RBKS. RBKS belongs to the PfkB family of carbohydrate kinases which includes adenosine kinase (AK) and fructokinase. RBKS shares high structural similarity to AK and its catalytic mechanism is very similar to AK (Park & Gupta 2008).