Topaquinone (TPQ) is a

redox Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...

cofactor derived from the amino acid

tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the G ...

. Its name derives from 2,4,5-trihydroxyphenylalanine-quinone. Its structure was first identified in 1990.{{Cite journal, title = Structure and biogenesis of topaquinone and related cofactors , journal = Journal of Biological Inorganic Chemistry , date = Feb 1999, issn = 0949-8257, pmid = 10499097, pages = 1–11, volume = 4, issue = 1, first = D. M., last = Dooley, doi = 10.1007/s007750050283 , s2cid = 10104769 It is used by copper

amine oxidase An amine oxidase is an enzyme that catalyzes the oxidative cleavage of alkylamines into aldehydes and ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictoge ...

s which contain a tyrosine residue near the active site. This residue catalyses its own transition, first to

dopaquinone -Dopaquinone also known as ''o''-dopaquinone is a metabolite of L-DOPA (L-dihydroxyphenylalanine) and a precursor of melanin. Biosynthesis of melanin occurs in melanocytes, where tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyph ...

and then to topaquinone, in a Cu²⁺ dependent manner.

References

Cofactors Alpha-Amino acids Amino acid derivatives 1,4-Benzoquinones Hydroxybenzoquinones Propionic acids