Biosynthesis of purine nucleotides
Purine nucleotides are synthesized in cytoplasm of most of the tissues. The major site for purine synthesis is liver. Since purine ring are synthesized from different small components, they are makorly denoted by de novo synthesis. Different
sources such as respiratory CO2, amino group from aspartate, formyl group,amide group from glutamine and glycine etc., are required for formation of purine ring. As a primary requirement of purine synthesis, purine ring are first built upon a ribose-5-phosphate molecule. De novo synthesis of purine is a multi enzyme reaction composed of 10 steps as follow as
In salvage pathway purines were recycled from degraded nucleotide. Both nucleosides and deoxy-nucleosides can be salvaged. Phospho ribosyl phyrophosphate (PRPP) is the starting material for salvage pathway. In salvage pathway purines are salvaged by adenine phosphor ribosyl transferase (APRTase) and hypoxanthine guanine phosphoribosyl transferase (HGPRTase). Salvage pathway are encountered in tissues such as RBC and brain, where there is absence of denovo pathway.
