Dopaquinone as a Common Intermediate in the Biogenesis of Tyrosine-Derived Quinone Cofactors

Abstract

Copper amine oxidases (CAOs) are essential for maintaining the level of biogenic amines in the body as well as being involved in the inflammation and immune responses. Lysyl oxidase (LOX), a member of CAO, plays an important role in stabilizing the extracellular matrix but its over-expression has been associated with metastasis/invasion of breast cancer cells. The biogeneses of the topaquinone (TPQ) cofactor of CAO and the lysine tyrosylquinone (LTQ) cofactor in LOX from the corresponding Tyr residue are self-catalyzed processes requiring copper and O2. In CAO, a putative dopaquinone (DPQ) intermediate has been proposed to react with a copper-associated water molecule, through a 1,4-addition mechanism, leading to the formation of TPQ. The D298K mutant of a bacterial CAO produces an iminoquinone tautomer (LTI) of lysine tyrosylquinone (LTQ). The results of this study strongly support the proposal that DPQ is a common intermediate in the biogenesis of these tyrosine-derived cofactors.