Effects of divalent cations on nadh‐linked electron transfer in corn root plasma membrane

Abstract

The effects of calcium (Ca²⁺), cadmium (Cd²⁺), and copper (Cu²⁺) cations on NADH‐linked electron transfer in com root plasma membrane vesicles were investigated. The reduction of both cytochrome c and ferricyanide were slightly stimulated by Ca²⁺ but not significantly affected by Cd²⁺. However, Cd²⁺ induced a redox‐linked increase in light scattering suggesting an increase in the size/volume of the vesicles. The presence of micromolar levels of Cu²⁺ decreased the reduction rates of both cytochrome c and ferricyanide. However, in contrast to ferricyanide reduction, Cu inhibition to the cytochrome c reduction was more effective, and was less sensitive to ionic strength. Copper inhibition changed the Michaelis‐Menten dependence of the ferricyanide reduction but not that of cytochrome c. These results suggest that the reduction of cytochrome c. and ferricyanide must occur at different membrane sites.

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Shu‐I Tu

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