Product Code Database
Ribose is a simple sugar and carbohydrate with molecular formula C5H10O5 and the linear-form composition H−(C=O)−(CHOH)4−H. The naturally occurring form, , is a component of the from which RNA is built, and so this compound is necessary for Genetic code, decoding, Regulatory RNA and RNA splicing of . It has a structural analog, deoxyribose, which is a similarly essential component of DNA. is an unnatural sugar that was first prepared by Emil Fischer and Oscar Piloty in 1891. It was not until 1909 that Phoebus Levene and Walter Jacobs recognised that was a natural product, the enantiomer of Fischer and Piloty's product, and an essential component of . Fischer chose the name "ribose" as it is a partial rearrangement of the name of another sugar, arabinose, of which ribose is an epimer at the 2' carbon; both names also relate to gum arabic, from which arabinose was first isolated and from which they prepared .
Like most sugars, ribose exists as a mixture of cyclic compound in equilibrium with its linear form, and these readily interconvert especially in aqueous solution. The name "ribose" is used in biochemistry and biology to refer to all of these forms, though more specific names for each are used when required. In its linear form, ribose can be recognised as the pentose sugar with all of its hydroxyl on the same side in its Fischer projection. has these hydroxyl groups on the right hand side and is associated with the systematic name (2 R,3 R,4 R)-2,3,4,5-tetrahydroxypentanal, whilst has its hydroxyl groups appear on the left hand side in a Fischer projection. Cyclisation of ribose occurs via hemiacetal formation due to attack on the aldehyde by the C4' hydroxyl group to produce a furanose form or by the C5' hydroxyl group to produce a pyranose form. In each case, there are two possible geometric outcomes, named as α- and β- and known as , depending on the stereochemistry at the hemiacetal carbon atom (the "anomeric carbon"). At room temperature, about 76% of is present in pyranose forms (α:β = 1:2) and 24% in the furanose forms (α:β = 1:3), with only about 0.1% of the linear form present. (1997). 9780120026449 ISBN 9780120026449
The adenosine, cytidine, guanosine, and uridine are all derivatives of β--ribofuranose. Metabolism species that include phosphorylated ribose include ADP, ATP, coenzyme A, and NADH. cAMP and cGMP serve as secondary messengers in some signaling pathways and are also ribose derivatives. The ribose moiety appears in some pharmaceutical agents, including the antibiotics neomycin and paromomycin.
Ribose can be synthesized chemically, but commercial production relies on fermentation of glucose. Using genetically modified strains of B. subtilis, 90 g/liter of ribose can be produced from 200 g of glucose. The conversion entails the intermediacy of gluconate and ribulose.
The "-" in the name -ribose refers to the stereochemistry of the chiral carbon atom farthest away from the aldehyde group (C4'). In -ribose, as in all -sugars, this carbon atom has the same configuration as in D-glyceraldehyde.
For ribose residues in and nucleotide, the torsion angles for the rotation encompassing the bonds influence the configuration of the respective nucleoside and nucleotide. The secondary structure of a nucleic acid is determined by the rotation of its 7 . Having a large amount of torsion angles allows for greater flexibility.
In closed ring riboses, the observed flexibility mentioned above is not observed because the ring cycle imposes a limit on the number of torsion angles possible in the structure. Conformers of closed form riboses differ in regards to how the lone oxygen in the molecule is positioned respective to the nitrogenous base (also known as a nucleobase or just a base) attached to the ribose. If a carbon is facing towards the base, then the ribose is labeled as endo. If a carbon is facing away from the base, then the ribose is labeled as exo. If there is an oxygen molecule attached to the 2' carbon of a closed cycle ribose, then the exo confirmation is more stable because it decreases the interactions of the oxygen with the base. The difference itself is quite small, but when looking at an entire chain of RNA the slight difference amounts to a sizable impact.
One important modification occurs at the C2' position of the ribose molecule. By adding an Alkyl group, the nuclear resistance of the RNA is increased because of additional stabilizing forces. These forces are stabilizing because of the increase of Hydrogen bonding and an increase in the glycosidic bond stability. The resulting increase of resistance leads to increases in the half-life of siRNA and the potential therapeutic potential in cells and animals. The methylation of ribose at particular sites is correlated with a decrease in immune stimulation.
Similar to the 2' modifications in nature, a synthetic modification of ribose includes the addition of fluorine at the 2' position. This fluorinated ribose acts similar to the methylated ribose because it is capable of suppressing immune stimulation depending on the location of the ribose in the DNA strand. The big difference between methylation and fluorination, is the latter only occurs through synthetic modifications. The addition of fluorine leads to an increase in the stabilization of the glycosidic bond and an increase of intramolecular hydrogen bonds.
Supplemental -ribose can bypass part of the pentose phosphate pathway, an energy-producing pathway, to produce -ribose-5-phosphate. The enzyme glucose-6-phosphate-dehydrogenase (G-6-PDH) is often in short supply in cells, but more so in diseased tissue, such as in Cardiac muscle cells in patients with cardiac disease. The supply of -ribose in the Mitochondrion is directly correlated with ATP production; decreased -ribose supply reduces the amount of ATP being produced. Studies suggest that supplementing -ribose following tissue ischemia (e.g. myocardial ischemia) increases myocardial ATP production, and therefore mitochondrial function. Essentially, administering supplemental -ribose bypasses an enzymatic step in the pentose phosphate pathway by providing an alternate source of 5-phospho--ribose 1-pyrophosphate for ATP production. Supplemental -ribose enhances recovery of ATP levels while also reducing cellular injury in humans and other animals. One study suggested that the use of supplemental -ribose reduces the instance of angina in men with diagnosed coronary artery disease. -Ribose has been used to treat many pathological conditions, such as chronic fatigue syndrome, fibromyalgia, and myocardial dysfunction. It is also used to reduce symptoms of cramping, pain, stiffness, etc. after exercise and to improve athletic performance.
|
|
