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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 ).
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]
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.
A key regulatory step is the production of 5-phospho-α-D-ribosyl 1-pyrophosphate by ribose-phosphate diphosphokinase, which is activated by inorganic phosphate and inactivated by purine ribonucleotides. It is not the committed step to purine synthesis because PRPP is also used in pyrimidine synthesis and salvage pathways.
The 3 substrates of this enzyme are ATP, ribose 5-phosphate, and NH 3, whereas its 3 products are ADP, phosphate, and 5-phosphoribosylamine. This enzyme belongs to the family of ligases, specifically those forming generic carbon-nitrogen bonds. The systematic name of this enzyme class is ribose-5-phosphate:ammonia ligase (ADP-forming).
The enzyme is involved in the synthesis of nucleotides (purines and pyrimidines), cofactors NAD and NADP, and amino acids histidine and tryptophan, [1] [2] [3] linking these biosynthetic processes to the pentose phosphate pathway, from which the substrate ribose 5-phosphate is derived. Ribose 5-phosphate is produced by the pentose phosphate ...
In enzymology, a ribose-5-phosphate adenylyltransferase (EC 2.7.7.35) is an enzyme that catalyzes the chemical reaction. ADP + D-ribose 5-phosphate phosphate + ADP-ribose. Thus, the two substrates of this enzyme are ADP and D-ribose 5-phosphate, whereas its two products are phosphate and ADP-ribose.