5'-Guanylic acid is involved in several metabolic disorders, including AICA-ribosiduria pathway, ?adenosine deaminase deficiency,adenine phosphoribosyltransferase deficiency (aprt), and the 2-hydroxyglutric aciduria pathway.

Glycerol 3-phosphate biscyclohexylammonium salt is an endogenous metabolite produced by cytosolic glycerol 3-phosphate dehydrogenase pathway.

Pyrrole-2-carboxylic acid was first identified as a degradation product of sialic acids then as a derivative of the oxidation of the D-hydroxyproline isomers by mammalian D-amino acid oxidase.