Hydrogen abstraction galactose oxidase

Fig. 21. Proposed catalytic mechanism for substrate oxidation by galactose oxidase. (A) Substrate binding displaces Tyr-495 phenolate which serves as a general base for abstracting the hydroxylic proton. (B) Stererospecihc pro- hydrogen abstraction by the Tyr-Cys phenoxyl radical. (C) Inner sphere electron transfer reducing Cu(II) to Cu(I). (D) Dissociation of the aldehyde product.

A putative Cu -hydroxo species, generated as in Eq. (20) of Fig. 14, could also be able to oxidize DNA as in Eqs. (21,22), since this trivalent state of copper has been observed when it is stabilized by a ligand having strong a donor effects as hydroxyl or deprotonated amides it was involved in biological processes like in the case of the galactose oxidase reaction (134-136). In this pathway, the Cu -hydroxo species abstracts a hydrogen atom on DNA to form a radical and a Cu complex [Eq. (21)]. Then an electron transfer... 

Hydrogen atom abstraction by Cu(II)- and Zn(II)-phenoxyl radical complexes was used as a model for the active form of galactose oxidase (Taki et al. 2000). 

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