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Crystal structure of ribose 5-phosphate isomerase and ribose 5-phosphate complex in E. coli. R5P consists of a five-carbon sugar, ribose, and a phosphate group at the five-position carbon. It can exist in open chain form or in furanose form. The furanose form is most commonly referred to as ribose 5-phosphoric acid. [1]
Ribose-5-phosphate isomerase (Rpi) encoded by the RPIA gene is an enzyme (EC 5.3.1.6) that catalyzes the conversion between ribose-5-phosphate (R5P) and ribulose-5-phosphate (Ru5P). It is a member of a larger class of isomerases which catalyze the interconversion of chemical isomers (in this case structural isomers of pentose ).
L-Ribose Fischer Projection. Ribose is a simple sugar and carbohydrate with molecular formula C 5 H 10 O 5 and the linear-form composition H−(C=O)−(CHOH) 4 −H. The naturally occurring form, d-ribose, is a component of the ribonucleotides from which RNA is built, and so this compound is necessary for coding, decoding, regulation and expression of genes.
The pentose phosphate pathway. The pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt or HMP shunt) is a metabolic pathway parallel to glycolysis. [1] It generates NADPH and pentoses (five-carbon sugars) as well as ribose 5-phosphate, a precursor for the synthesis of nucleotides. [1]
ADP is the key allosteric inhibitor of ribose-phosphate diphosphokinase. It has been shown that at lower concentrations of the substrate ribose 5-phosphate, ADP may inhibit the enzyme competitively. Ribose-phosphate pyrophosphokinase is also inhibited by some of its downstream biosynthetic products. [2] [6]
[1] [2] [3] The vitamins thiamine [4] and cobalamin, [5] and the amino acid tryptophan also contain fragments derived from PRPP. [6] It is formed from ribose 5-phosphate (R5P) by the enzyme ribose-phosphate diphosphokinase: [7] It plays a role in transferring phospho-ribose groups in several reactions, some of which are salvage pathways: [8]
Beta-D-ribofuranose can then be converted to ribose-5-phosphate. In the images on the right, both structures have five carbons but differ in the amount of hydrogens by one, oxygens by three, and phosphorus by one. The key difference is the group on carbon four. From here, ribose 5-phosphate can enter into the pentose phosphate pathway (PPP). [4]
Ribose is a constituent of RNA, and the related molecule, deoxyribose, is a constituent of DNA. Phosphorylated pentoses are important products of the pentose phosphate pathway , most importantly ribose 5-phosphate (R5P), which is used in the synthesis of nucleotides and nucleic acids , and erythrose 4-phosphate (E4P), which is used in the ...