Reticulocyte lipoxygenase changes the passive electrical properties of bovine heart submitochondrial particles.

ABSTRACT

Purified reticulocyte lipoxygenase oxygenates the polyunsaturated phospholipids of sonified submitochondrial particles from bovine heart as measured by a burst of oxygen uptake. Over the frequency range of 0.5 to 100 MHz, the complex impedance of the submitochondrial particles as a function of the frequency before and after lipoxygenase attack was measured. From these data, the membrane capacity, the conductivity of the membrane and the conductivity inside the particles were calculated. Lipoxygenase action causes a 4-fold increase in the membrane capacity and a 2-fold increase in the membrane conductivity. Using the method of deformation of electric pulses, kinetic measurements were performed. In parallel to the changes of the passive electric properties, a partial inhibition of NADH oxidase and succinate oxidase was caused by the lipoxygenase attack. Oxygen uptake, changes of the passive electric properties and the inhibition of respiratory enzymes were prevented by lipoxygenase inhibitors. Owing to the high oxygen consumption produced by the lipoxygenase reaction, anaerobiosis was reached within the first 30 s in the closed chamber. Therefore, it must be concluded that the changes in passive electric properties and the inhibition of the respiratory enzymes are due to secondary anaerobic processes such as the hydroperoxidase reaction catalyzed by the lipoxygenase or a slow redistribution of peroxidized membrane lipids. The results are discussed in relation to the breakdown of mitochondria during the maturation process of red cells.