Changes induced by hydrazine in optical spectra of cytochrome oxidase

Abstract

Under aerobic conditions hydrazine reduces haem a of cardiac cytochrome oxidase and brings about the formation in optical spectra of a new band at 845 nm, whereas under anaerobic conditions hydrazine reduces both haems, a and a ₃, as well as EPR-detectable copper, Cu_A, and results in the band at 845 nm. The formation of this band was sensitive to inhibitors of oxygen binding. It is suggested that the band at 845 nm reflects changes induced by hydrazine in Cu_B which in the resting enzyme is EPR-undetectable.