InterPro domain: IPR002139

Ribokinases participate in the first step of ribose metabolism, and are members of the superfamily of carbohydrate kinases. Ribokinases phosphorylate ribose to ribose-5-phosphate in the presence of ATP and magnesium [ 1 ]:

ATP + D-Ribose = ADP + D-Ribose-5-Phosphate

The phosphorylated sugar may then enter the pentose phosphate pathway [ 2 ]. There are indications that the phosphorylated sugar may also be used in the synthesis of amino acids (histidine and tryptophan). Further, links to mammalian adenosine kinase have been identified, through sequence similarity, suggesting possible homology [ 3 , 3 ].

This family also includes fructokinases [ 4 ]. Fructokinase may be involved in a sugar-sensing pathway in plants [ 5 , 6 ].

This family also includes cytidine kinase from Thermococcus kodakarensis [ 7 ] and MJ0406 ( Q57849 ) from Methanocaldococcus jannaschii. MJ0406 was previously annotated as a 6-phosphofructokinases (PFK), but has since been characterised as a functional nucleoside kinase [ 8 ].

1. Purification, characterization, and crystallization of Escherichia coli ribokinase. Protein Sci. 6, 2474-6
2. Cloning of human adenosine kinase cDNA: sequence similarity to microbial ribokinases and fructokinases. Proc. Natl. Acad. Sci. U.S.A. 93, 1232-7
3. Cloning and characterization of cDNA for adenosine kinase from mammalian (Chinese hamster, mouse, human and rat) species. High frequency mutants of Chinese hamster ovary cells involve structural alterations in the gene. Eur. J. Biochem. 241, 564-71
4. Convergent evolution of similar enzymatic function on different protein folds: the hexokinase, ribokinase, and galactokinase families of sugar kinases. Protein Sci. 2, 31-40
5. Plant fructokinases: a sweet family get-together. Trends Plant Sci. 5, 531-6
6. Isolation and characterization of two fructokinase cDNA clones from rice. Phytochemistry 62, 47-52
7. A pentose bisphosphate pathway for nucleoside degradation in Archaea. Nat Chem Biol 11, 355-60
8. The phosphofructokinase-B (MJ0406) from Methanocaldococcus jannaschii represents a nucleoside kinase with a broad substrate specificity. Extremophiles 11, 105-14