Topaquinone

Names
IUPAC name (2S)-2-Amino-3-(4-hydroxy-3,6-dioxocyclohexa-1,4-dien-1-yl)propanoic acid
Other names 6-Hydroxydopaquinone
Identifiers
CAS Number	64192-68-3
PubChem CID	123871
CompTox Dashboard (EPA)	DTXSID40982735
Properties
Chemical formula	C9H9NO5
Molar mass	211.173 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Topaquinone (TPQ) is a redox cofactor derived from the amino acid tyrosine. Its name derives from 2,4,5-trihydroxyphenylalanine-quinone. Its structure was first identified in 1990.^[1] It is used by copper amine oxidases which contain a tyrosine residue near the active site. This residue catalyses its own transition, first to dopaquinone and then to topaquinone, in a Cu²⁺ dependent manner.^[1]