Effect of monovalent cations on the inhibition by NAD + of NADH oxidation in submitochondrial particles

Abstract

Oxidation of NADH in submitochondrial particles, with O 2 or ferricyanide as electron acceptor, was inhibited by micromolar concentrations of NAD + when measured in 240 mM sucrose or, in a lesser extent, in 120 mM NaCl or LiCl. In 120 mM solutions of either KCl, RbCl, CsCl or NH 4Cl the inhibition by up to 100 μM concentrations of NAD + did not occur. The inhibition observed in the sucrose medium disappeared after solubilization of the particles with detergents and re-appeared when the membranes were reconstituted. The inhibitory effect was potentiated by palmitoyl-CoA. The possibility is discussed that the inhibition of NADH oxidation by low concentrations of NAD + and its release by K +, Rb +, Cs + and NH 4 + depend on the interaction between NAD + and the negatively charged mitochondrial membrane.