Diazene-A Not-So-Innocent Ligand for the Binuclear Center of Cytochrome Oxidase

Guang-Ling Liao and Graham Palmer
Biochemistry in review, 1998

SUMMARY: Diazene reacts rapidly with cytochrome c oxidase to reduce cytochrome a and CuA and to form a charge transfer complex with ferric cytochrome a3; the diazene may serve to bridge the heme iron of this cytochrome and CuB. The complex is characterized by an intense, optically active absorbance located at 847 nm. A similar band had been observed previously upon reduction of cytochrome oxidase with hydrazine (Markossian, K. A., Paitian, N. A. & Nalbandyan, R. M. (1983) FEBS Lett. 156, 235-238) but it appears that this band is actually due to the diazene produced as a result of the oxidation of the hydrazine which occurs in this process. A similar diazene-to-iron chargeÐtransfer band is found following reaction of diazene with ferric horseradish peroxidase and with hemin chloride, but not with metÐmyoglobin.