Purine Salvage Pathway

INTRODUCTION:
  • This pathway ensures the recycling of purines formed by degradation of nucleotides.
  • Nucleosides & deoxy-nucleosides can also be salvaged.
  • Salvage pathway of purine nucleotide synthesis are used by Brain, RBC,Leukocytes
  • The purines can be directly converted to the corresponding nucleotides & this process is known as ‘salvage pathway’.
  • PRPP is the starting material in this pathway.
  • It is also a substrate for de novo synthesis.
  • The purines salvage pathway is for Hypoxanthine and Adenine
  • The free purines are salvaged by two different enzymes.
  1. Adenine phospho ribosyl transferase (APRTase).
  2. Hypoxanthine guanine phosphoribosyl transferase (HGPRTase).
  • Adenine phosphoribosyl transferase catalyses the formation of AMP from adenine.
  • First purine nucleotide, which is synthesized in purine biosynthesis is IMP
  • Hypoxanthine-guanine phosphoribosyl transferase (HGPRT) converts guanine & hypoxanthine to GMP & IMP.
  • Phosphoribosyl pyrophosphate (PRPP) is the donor of ribose 5-phosphate in the salvage pathway.


IMPORTANCE OF SALVAGE PATHWAY:
  • The salvage pathway is particularly important in certain tissues such as erythrocytes & brain where de novo (a new) synthesis of purine nucleotides is not operative.
  •  A defect in the enzyme HGPRT causes Lesch - Nyhan syndrome.
Exam Question of:
  • The purines salvage pathway is for Hypoxanthine and Adenine
  • First purine nucleotide, which is synthesized in purine biosynthesis is IMP
  • Salvage pathway of purine biosynthesis is important for RBCs
  • PRPP glutamyl amidotransferase is increased to increase purine synthesis in Liver
  • Salvage pathway of purine nucleotide synthesis are used by Brain, RBC,Leukocytes

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