A salvage pathway is a pathway in which a biological product is produced from intermediates in the degradative pathway of its own or a similar substance. The term often refers to nucleotide salvage in particular, in which nucleotides (purine and pyrimidine) are synthesized from intermediates in their degradative pathway.
Nucleotide salvage pathways are used to recover bases and nucleosides that are formed during degradation of RNA and DNA. This is important in some organs because some tissues cannot undergo de novo synthesis. The salvaged products can then be converted back into nucleotides. Salvage pathways are targets for drug development, one family being called antifolates. its deficiency is implicated in Lesch–Nyhan syndrome.
{| class="wikitable"
! Nucleobase !! Enzyme !! Nucleotide
|-
| hypoxanthine || hypoxanthine/guanine phosphoribosyl transferase (HGPRT) || IMP
|-
| guanine || hypoxanthine/guanine phosphoribosyl transferase (HGPRT) || GMP
|-
| adenine || adenine phosphoribosyltransferase (APRT) || AMP
|}
Folate biosynthesis
Tetrahydrofolic acid and its derivatives are produced by salvage pathways from GTP.
Other salvage pathways
L-methionine salvage is the pathway that regenerates methionine from its downstream products. A version of the pathway uses methylthioadenosine (MTA), forming the so-called MTA cycle with its synthesizing reaction. This sulphur-recycling action is found in humans, and seems to be universal among aerobic life.
Nicotinate salvage is the process of regenerating nicotinamide adenine dinucleotide from nicotinic acid. This pathway is important for controlling the level of oxidative stress in cells. The human gene NAPRT encodes the main enzyme in the pathway. Cancer cells, which have increased NAD requirements, tend to upregulate the pathway.
Salvage pathways also exist for ceramide, cobalamin, cell wall components, and tetrahydrobiopterin in various organisms.