Stizolobic acid is an amino acid found in the sap epicotyl tips of etiolated seedlings of Stizolobium hassjoo - Mucuna pruriens.
Stizolobium hassjoo contains the enzyme stizolobate synthase which catalyzes the conversion of L-DOPA into stizolobic acid in the presence of oxidised nicotinamide adenine dinucleotide as a cofactor, under aerobic conditions.
The initial product is 4-(L-alanin-3-yl)-2-hydroxy-cis,cis-muconate 6-semialdehyde.
The intermediate readily cyclises and further oxidises, forming a 2-pyrone ring; this is stizolobic acid, which is the product that is isolated and after which this enzyme is named.
A separate enzyme, stizolobinate synthase also present in higher plants cleaves L-DOPA in a way which produces the isomeric compound, stizolobinic acid.