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Ribose

Ribose, is an organic compound with formula C₅H₁₀O₅; specifically, a monosaccharide (simple sugar) with linear form H-(C=O)-(CHOH)₄-H, which has all the hydroxyl groups on the same side in the Fischer projection.

The term may refer to any of two enantiomers: almost always to D-ribose, that occurs widely in nature and is discussed here; or to its synthetic mirror image L-ribose, which is not found in nature and is of limited interest.

D-ribose was first reported in 1891 by Emil Fischer. It comprises the backbone of RNA, a biopolymer that is the basis of genetic transcription. It is related to deoxyribose, as found in DNA. Once phosphorylated, ribose can become a subunit of ATP, NADH, and several other compounds that are critical to metabolism.

Structure

Ribose is an aldopentose, that is a monosaccharide containing five carbon atoms that, in its acyclic form, has an aldehyde functional group at one end. In the conventional numbering scheme for monosaccharides, the carbon atoms are numbered from C1' (in the aldehyde group) to C5'. The deoxyribose derivative, found in DNA, differs from ribose by having an hydrogen atom in place of the hydroxyl group in carbon C2'.

Like many monosaccharides, ribose occurs in water as the linear form H-(C=O)-(CHOH)₄-H and any of two ring forms: ribofuranose ("C3'-endo"), with a five-membered ring, and ribopyranose ("C2'-endo"), with a six-membered ring. The ribofuranose form is predominant.

The "D-" in the name D-ribose refers to the stereochemistry of the chiral carbon atom farthest away from the aldehyde group (C4'). In D-ribose, as in all D-sugars, this carbon atom has the same configuration as in D-glyceraldehyde.

Phosphorylation

In biology, D-ribose must be phosphorylated by the cell before it can be used. Ribokinase catalyzes this reaction by converting D-ribose to D-ribose 5-phosphate. Once converted, D-ribose-5-phosphate is available for the manufacturing of the amino acids tryptophan and histidine, or for use in the pentose phosphate pathway.

Use as a supplement

D-ribose is often marketed as a supplement for bodybuilders with a common recommended daily dose being 5�g, even though some studies have found no evidence there is a benefit, others have found increased endurance, recovery and muscle output in healthy individuals.

D-ribose has also been used to reduce fatigue in fibromyalgia and chronic fatigue syndrome. A 2006 pilot study concluded that D-ribose (5�g three times a day) was effective in the treatment of FM and CFS.. Although this study lacked any control group because essentially everyone involved was literally taking sugar pills, the authors reported that 66% of the 41 participants found the supplement helpful and it produced improvement in all the areas tested: energy, sleep, mental clarity, pain intensity, and well-being. Without further study, it is unclear if this is a substantial effect, or a placebo effect. In addition, there is no transporter or uptake mechanism for ribose in the intestine. The energy yield comes from two- and three-carbon compounds created when ribose is fermented by intestinal bacteria.

Source: Wikipedia