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A salvage pathway is a pathway in which a biological product is produced from intermediates in the degradative pathway of its own or a similar substance. The term often refers to nucleotide salvage in particular, in which nucleotides ( purine and pyrimidine ) are synthesized from intermediates in their degradative pathway.
It is a biochemical intermediate in the formation of purine nucleotides via inosine-5-monophosphate, as well as in pyrimidine nucleotide formation. Hence it is a building block for DNA and RNA. [1] [2] [3] The vitamins thiamine [4] and cobalamin, [5] and the amino acid tryptophan also contain fragments derived from PRPP. [6]
It is not the committed step to purine synthesis because PRPP is also used in pyrimidine synthesis and salvage pathways. The first committed step is the reaction of PRPP, glutamine and water to 5'-phosphoribosylamine (PRA), glutamate , and pyrophosphate - catalyzed by amidophosphoribosyltransferase , which is activated by PRPP and inhibited by ...
Pyrimidine degradation ultimately ends in the formation of ammonium, water, and carbon dioxide. The ammonium can then enter the urea cycle which occurs in the cytosol and the mitochondria of cells. [5] Pyrimidine bases can also be salvaged. For example, the uracil base can be combined with ribose-1-phosphate to create uridine monophosphate or UMP.
[7] [13] [14] Inhibition occurs via a structural change in the enzyme where the flexible glutamine loop gets locked in an open position, preventing the binding of PRPP. [ 7 ] Due to the chemical lability of PRA, which has a half-life of 38 seconds at pH 7.5 and 37 °C, researchers have suggested that the compound is channeled from ...
The product of this reaction, phosphoribosyl pyrophosphate (PRPP), is used in numerous biosynthesis (de novo and salvage) pathways. PRPP provides the ribose sugar in de novo synthesis of purines and pyrimidines, used in the nucleotide bases that form RNA and DNA. PRPP reacts with orotate to form orotidylate, which can be converted to uridylate ...
Formation of PRPP is essential for both the de novo synthesis of purines and for the purine salvage pathway. [8] The de novo synthesis pathway begins with the activation of R5P to PRPP, which is later catalyzed to become phosphoribosylamine, a nucleotide precursor. During the purine salvage pathway, [9] phosphoribosyltransferases add PRPP to ...
CTP (cytidine triphosphate) synthetase catalyzes the last committed step in pyrimidine nucleotide biosynthesis: [3] ATP + UTP + glutamine → ADP + P i + CTP + glutamate . It is the rate-limiting enzyme for the synthesis of cytosine nucleotides from both the de novo and uridine salvage pathways.