Figure 1.

DPQ is proposed as a common intermediate in the biogenesis of TPQ and LTQ. 1,4−Hydration or 1,4−amination of DPQ followed by O₂ oxidation yield TPQ or LTQ. DPQ detected during biogenesis of TPQ in AGAO by X−ray snapshot analysis [7] and an LTQ−like quinone (K298 crosslinked to DPQ382) detected in D298K−AGAO [10] are also shown. DPQ382, Tyr284 (conserved Tyr) and Asp298 (active site base): in green; Cu²⁺ binding site (His431−X−His433-----His592): in brown; Val282 and Asn381 (walls of the wedge identified in CAOs [11,12]): in gray.