Reference work entry
Ribose is a five-carbon monosaccharide with three chiral centers (aldopentose) found in ribonucleic acid (RNA) and several coenzymes (ATP, B 12, NAD(P)H, etc.) with the formula (C 5H 10O 5). Ribose has all the hydroxyl groups on the same side in the Fischer projection. Ribose can exist in two enantiomeric forms, D and L. Biological nucleic acids use the D version. Ribose is the precursor to deoxyribose in biology. In water, ribose exists in equilibrium as furanose, open-chain, and pyranose forms (from left to right in Fig. 1). The pyranose form is predominant (76 %). d-Ribose must be phosphorylated to d-ribose 5-phosphate before it can be used by the cell’s enzymes. Ribokinase catalyzes this reaction. Once phosphorylated, d-ribose-5-phosphate is used for the biosynthesis of the amino acids tryptophan and histidine and in the pentose phosphate pathway. d-Ribose 5-phosphate is further converted to phosphoribosyl pyrophosphate for the biosynthesis of nucleotides.
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