Effects of Several Cl- and NO₃-salts on the Monoamine Oxidase in Hog Brain Mitochondrial Membrane

Abstract

Inhibitory effects of several chlorides (NaCl, KCl, LiCl and CaCl₂) and nitrates (NaNO₃, KNO₃, Ca (NO₃) ₂, Ba (NO₃) ₂ and Mg (NO₃) ₂) on the activities of monoamine oxidase (MAO) were studied in mitochondrial membrane preparations obtained by hypotonic treatment of mitochondria from the brain of hogs. The MAO activities were determined according to a modification of McEwen's method by measuring the benzaldehyde produced by enzymatic oxidation of the substrate benzylamine. All the chlorides strongly inhibited MAO activity. It was shown that the inhibition was not attributable to the positive ions such as Na⁺, K⁺ and Li⁺, but that negative ions such as Cl^- and NO₃^- were responsible for the effects. The NO₃^- ions all showed 10 times the inhibitory effects of the Cl^- ions. Analysis of the double-reciprocal Lineweaver-Burk plots revealed that all of the inhibitory actions were non-competitive and reversible.