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
Purines are biologically synthesized as nucleotides and
in particular as ribotides, i.e. bases attached to ribose5-phosphate.

Purines are synthesized by two types of pathways, the
de novo pathways and the salvage pathways.

De novo synthesis of purines begins with the metabolic
precursors like amino acids, ribose-5-phosphate, CO2
and NH3.

Salvage pathways recycle the free bases and
nucleosides released from nucleic acid breakdown.

The purine ring structure is first built up to one or few
atoms and then attached to ribose sugar to form
nucleotides.

Amino acid glycine is an important precursor in
purine synthesis, aspartate is also used as source of
amino group.

The enzymes for de novo synthesis are present as
large, multienzyme complexes in the cell.

The two parent purine nucleotides are adenosine
monophosphate (AMP; adenylate) and guanosine
monophosphate (GMP; guanylate)

A key regulatory step is the production of 5phosphoribosyl-1-pyrophosphate (PRPP) by PRPP
synthetase.
DE NOVO
SYNTHESIS OF
PURINES
ENZYMES USED
ENZYMES USED
Purines from nucleic acids or from food can also be
salvaged and reused in new nucleotides.
 The brain is especially dependent on the salvage
pathway .
 The enzyme adenine phosphoribosyltransferase
(APRT) salvages adenine.
 The enzyme hypoxanthine-guanine
phosphoribosyltranferase (HGPRT) salvages
hypoxanthine and guanine. Genetic deficiency of
HGPRT leads to Lesch-Nyhan Syndrome in male
children.
Adenine + PRPP  AMP + PPi
