A specific role for Ca2+ in the oxidation of exogenous NADH by Jerusalem-artichoke (Helianthus tuberosus) mitochondria

Biochem J. 1981 Feb 15;194(2):487-95. doi: 10.1042/bj1940487.

Abstract

1. The addition of chelators to a suspension of mitochondria in a low-cation medium containing 9-aminoacridine caused a decrease in 9-aminoacridine fluorescence. The chelators removed bivalent cations from the membranes and allowed more 9-aminoacridine to move into the diffuse layer. The relative effect of EGTA and EDTA on the fluorescence suggested that the mitochondria are isolated with about equal amounts of Ca2+ and Mg2+ on the membranes. 2. The removal of the bivalent ions by chelators resulted in the inhibition of NADH oxidation. The inhibition could not be removed by adding sufficient decamethylenebistrimethylammonium ion (DM2+) to screen the fixed charges on the membranes and restore the fluorescence of 9-aminoacridine. This observation suggests that bivalent metal ions have a specific role in the oxidation of NADH. 3. Ca2+ and not Mg2+ reversed the inhibition of NADH oxidation caused by EGTA, whereas both reversed the inhibition caused by EDTA. This suggests that Ca2+ plays a specific role and that Mg2+ reverses the inhibition caused by EDTA by displacing the bound calcium from the chelator. 4. The results are interpreted as showing that Ca2+ plays a specific role in the oxidation of external NADH in addition to its ability to screen electrostatically or bind to the fixed charges associated with the surface of the membrane.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminacrine
  • Calcium / metabolism*
  • Edetic Acid / pharmacology
  • Egtazic Acid / pharmacology
  • Helianthus / drug effects
  • Helianthus / metabolism*
  • Helianthus / ultrastructure
  • Magnesium / metabolism
  • Mitochondria / metabolism*
  • NAD / metabolism*
  • Oxidation-Reduction

Substances

  • NAD
  • Egtazic Acid
  • Aminacrine
  • Edetic Acid
  • Magnesium
  • Calcium