BIOCHEMISTRY - Textbook - Ostapchenko L. I. - 2012

Chapter 10. NUCLEIC ACID METABOLISM

10.5. Nucleotide Biosynthesis

The Synthesis of purine and pyrimidine NUCLEOTIDES requires A large number of Enzymes and Energy Expenditure, and can be carried out by all organisms except for certain auxotrophic mutant microorganisms.

There are two pathways for the synthesis of purine and pyrimidine nucleotides:

✵ de novo

✵ salvage pathway (reutilization).

De novo nucleotide synthesis utilizes simpler metabolic precursors available within The Cell. This mechanism accounts for the majority of purine and pyrimidine nucleotides produced, satisfying about 90% of the cell's nucleotide requirements.

The salvage pathway involves the reutilization of nitrogenous bases or nucleosides derived from dietary intake and nucleic acid Catabolism. Salvage Pathways account for approximately 10-20% of the total pool of these compounds in the cell.

Formation of 5-phosphoribosyl-1-pyrophosphate. Phosphoribosyl pyrophosphate (PRPP) plays a central role in the synthesis of both purine and pyrimidine nucleotides. It is synthesized by transferring the β, γ-pyrophosphate group of ATP to carbon 1 of ribose-5-phosphate (Fig. 10.6). The reaction is catalyzed by PRPP synthetase.

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Fig. 10.6. Synthesis of phosphoribosyl pyrophosphate

Ribose-5-phosphate can be produced via the Reactions of the Pentose Phosphate Pathway of glucose METABOLISM or during nucleoside catabolism, in which nucleoside phosphorylase first converts nucleosides to ribose-1-phosphate, followed by The transfer of the phosphate group to the 5-position mediated by a specific mutase.

PRPP is also involved in the Biosynthesis of Purine nucleotides via the salvage pathway, the synthesis of nucleotide Coenzymes, and The biosynthesis of the Amino Acids Histidine and Tryptophan.