# Purine Salvage

**Purine Salvage** is a biochemical pathway that recycles partially degraded purine bases to reform purine nucleotides.

Purine salvage begins with the free nitrogenous bases, **hypoxanthine** and **guanine**. Guanine combines with **PRPP** to form **GMP**, whereas Hypoxanthine combines with PRPP to form **IMP**. IMP can then be interconverted with **AMP**. Therefore, salvage of AMP occurs through hypoxanthine.

Both salvage reactions with PRPP are catalyzed by **HGPRT** (hypoxanthine guanine phosphoribosyltransferase). Notably, [Lesch-Nyhan Syndrome](/content/view/4743/index.html) is caused by a defect of HGPRT and impairs purine salvage.

A less common purine salvage pathway begins with **adenine**, since adenine is **not** usually produced by purine degradation. Adenine combines with PRPP to form **AMP**, in a reaction catalyzed by **APRT** (adenine phosphoribosyltransferase).