<p>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 [<cite idref="PUB00005046"/>]:</p><reaction>ATP + D-Ribose = ADP + D-Ribose-5-Phosphate</reaction><p>The phosphorylated sugar may then enter the pentose phosphate pathway [<cite idref="PUB00004876"/>].</p><p>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 [<cite idref="PUB00004876"/>, <cite idref="PUB00001470"/>].</p>