A<unk>  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<unk>  in particular, in which<unk> s (purine and pyrimidine) are synthesized from intermediates in their degradative pathway.<unk>  pathways are used to recover bases and<unk> s that are formed during degradation of RNA and DNA. This is important in some organs because some tissues cannot undergo de novo synthesis. The<unk> d products can then be converted back into<unk> s.<unk>  pathways are targets for drug development, one family being called antifolates. A number of other biologically-important substances, like methionine and nicotinate, have their own<unk>  pathways to recycle parts of the molecule.
Nucleotide salvage
Pyrimidine metabolism
Mitochondrial biogenesis
Protein carbonylation
Proteolysis
Purine metabolism
Fatty acid metabolism
DNA condensation