Inactivation of Alkaline Phosphatase by O₂¹ Δg

Abstract

RECENT evidence¹ strongly supports the role of singlet oxygen (O₂¹ Δg) as the active intermediate in the photosensitized addition of molecular oxygen to unsaturated hydrocarbon substrates. Because the characteristics of this reaction are also exhibited by aerobic dye-sensitized inactivation of enzymes and other photobiological processes collectively described as photodynamic action^2,3, there is a clear indication that O₂¹ Δg may be the reactive species in these processes also, although the possibility of a direct interaction between the substrate and electronically excited dye molecule cannot be eliminated. We report here an investigation of the effect of O₂¹ Δg, generated in the absence of photosensitizing dye, on the enzyme alkaline phosphatase, in conditions in which enzyme activity is otherwise preserved.